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![Richard van der Hoff](/assets/img/avatar_default.png)
The intention here is to make it clearer which fields we can expect to be populated when: notably, that the _event_type etc aren't used for the synchronous impl of EventContext.
247 lines
8.5 KiB
Python
247 lines
8.5 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 2014-2016 OpenMarket Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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from six import iteritems
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import attr
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from frozendict import frozendict
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from twisted.internet import defer
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from synapse.logging.context import make_deferred_yieldable, run_in_background
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@attr.s(slots=True)
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class EventContext:
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"""
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Attributes:
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state_group (int|None): state group id, if the state has been stored
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as a state group. This is usually only None if e.g. the event is
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an outlier.
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rejected (bool|str): A rejection reason if the event was rejected, else
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False
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prev_group (int): Previously persisted state group. ``None`` for an
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outlier.
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delta_ids (dict[(str, str), str]): Delta from ``prev_group``.
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(type, state_key) -> event_id. ``None`` for an outlier.
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app_service: FIXME
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_current_state_ids (dict[(str, str), str]|None):
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The current state map including the current event. None if outlier
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or we haven't fetched the state from DB yet.
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(type, state_key) -> event_id
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_prev_state_ids (dict[(str, str), str]|None):
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The current state map excluding the current event. None if outlier
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or we haven't fetched the state from DB yet.
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(type, state_key) -> event_id
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"""
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state_group = attr.ib(default=None)
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rejected = attr.ib(default=False)
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prev_group = attr.ib(default=None)
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delta_ids = attr.ib(default=None)
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app_service = attr.ib(default=None)
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_prev_state_ids = attr.ib(default=None)
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_current_state_ids = attr.ib(default=None)
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@staticmethod
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def with_state(
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state_group, current_state_ids, prev_state_ids, prev_group=None, delta_ids=None
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):
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return EventContext(
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current_state_ids=current_state_ids,
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prev_state_ids=prev_state_ids,
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state_group=state_group,
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prev_group=prev_group,
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delta_ids=delta_ids,
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)
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@defer.inlineCallbacks
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def serialize(self, event, store):
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"""Converts self to a type that can be serialized as JSON, and then
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deserialized by `deserialize`
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Args:
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event (FrozenEvent): The event that this context relates to
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Returns:
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dict
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"""
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# We don't serialize the full state dicts, instead they get pulled out
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# of the DB on the other side. However, the other side can't figure out
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# the prev_state_ids, so if we're a state event we include the event
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# id that we replaced in the state.
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if event.is_state():
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prev_state_ids = yield self.get_prev_state_ids(store)
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prev_state_id = prev_state_ids.get((event.type, event.state_key))
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else:
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prev_state_id = None
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return {
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"prev_state_id": prev_state_id,
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"event_type": event.type,
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"event_state_key": event.state_key if event.is_state() else None,
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"state_group": self.state_group,
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"rejected": self.rejected,
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"prev_group": self.prev_group,
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"delta_ids": _encode_state_dict(self.delta_ids),
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"app_service_id": self.app_service.id if self.app_service else None,
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}
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@staticmethod
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def deserialize(store, input):
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"""Converts a dict that was produced by `serialize` back into a
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EventContext.
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Args:
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store (DataStore): Used to convert AS ID to AS object
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input (dict): A dict produced by `serialize`
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Returns:
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EventContext
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"""
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context = _AsyncEventContextImpl(
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# We use the state_group and prev_state_id stuff to pull the
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# current_state_ids out of the DB and construct prev_state_ids.
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prev_state_id=input["prev_state_id"],
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event_type=input["event_type"],
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event_state_key=input["event_state_key"],
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state_group=input["state_group"],
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prev_group=input["prev_group"],
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delta_ids=_decode_state_dict(input["delta_ids"]),
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rejected=input["rejected"],
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)
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app_service_id = input["app_service_id"]
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if app_service_id:
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context.app_service = store.get_app_service_by_id(app_service_id)
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return context
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@defer.inlineCallbacks
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def get_current_state_ids(self, store):
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"""Gets the current state IDs
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Returns:
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Deferred[dict[(str, str), str]|None]: Returns None if state_group
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is None, which happens when the associated event is an outlier.
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Maps a (type, state_key) to the event ID of the state event matching
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this tuple.
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"""
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yield self._ensure_fetched(store)
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return self._current_state_ids
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@defer.inlineCallbacks
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def get_prev_state_ids(self, store):
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"""Gets the prev state IDs
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Returns:
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Deferred[dict[(str, str), str]|None]: Returns None if state_group
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is None, which happens when the associated event is an outlier.
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Maps a (type, state_key) to the event ID of the state event matching
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this tuple.
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"""
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yield self._ensure_fetched(store)
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return self._prev_state_ids
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def get_cached_current_state_ids(self):
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"""Gets the current state IDs if we have them already cached.
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Returns:
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dict[(str, str), str]|None: Returns None if we haven't cached the
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state or if state_group is None, which happens when the associated
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event is an outlier.
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"""
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return self._current_state_ids
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def _ensure_fetched(self, store):
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return defer.succeed(None)
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@attr.s(slots=True)
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class _AsyncEventContextImpl(EventContext):
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"""
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An implementation of EventContext which fetches _current_state_ids and
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_prev_state_ids from the database on demand.
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Attributes:
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_fetching_state_deferred (Deferred|None): Resolves when *_state_ids have
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been calculated. None if we haven't started calculating yet
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_event_type (str): The type of the event the context is associated with.
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_event_state_key (str): The state_key of the event the context is
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associated with.
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_prev_state_id (str|None): If the event associated with the context is
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a state event, then `_prev_state_id` is the event_id of the state
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that was replaced.
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"""
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_prev_state_id = attr.ib(default=None)
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_event_type = attr.ib(default=None)
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_event_state_key = attr.ib(default=None)
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_fetching_state_deferred = attr.ib(default=None)
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def _ensure_fetched(self, store):
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if not self._fetching_state_deferred:
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self._fetching_state_deferred = run_in_background(
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self._fill_out_state, store
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)
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return make_deferred_yieldable(self._fetching_state_deferred)
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@defer.inlineCallbacks
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def _fill_out_state(self, store):
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"""Called to populate the _current_state_ids and _prev_state_ids
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attributes by loading from the database.
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"""
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if self.state_group is None:
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return
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self._current_state_ids = yield store.get_state_ids_for_group(self.state_group)
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if self._prev_state_id and self._event_state_key is not None:
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self._prev_state_ids = dict(self._current_state_ids)
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key = (self._event_type, self._event_state_key)
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self._prev_state_ids[key] = self._prev_state_id
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else:
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self._prev_state_ids = self._current_state_ids
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def _encode_state_dict(state_dict):
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"""Since dicts of (type, state_key) -> event_id cannot be serialized in
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JSON we need to convert them to a form that can.
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"""
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if state_dict is None:
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return None
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return [(etype, state_key, v) for (etype, state_key), v in iteritems(state_dict)]
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def _decode_state_dict(input):
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"""Decodes a state dict encoded using `_encode_state_dict` above
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"""
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if input is None:
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return None
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return frozendict({(etype, state_key): v for etype, state_key, v in input})
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