add boilerplate for second edition

first_edition/ebook_src/trees/simple_tree.py

@@ -0,0 +1,41 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+
+""" A class for a simple tree """
+
+class SimpleTree(object):
+
+    def __init__(self, value=None, children = None):
+        self.value = value
+        self.children = children
+        if self.children == None:
+            self.children = []
+
+    def __repr__(self, level=0):
+        ret = "\t"*level+repr(self.value)+"\n"
+        for child in self.children:
+            ret += child.__repr__(level+1)
+        return ret
+
+
+
+def main():
+    """
+    'a'
+	    'b'
+		    'd'
+		    'e'
+	    'c'
+		    'h'
+		    'g'
+    """
+    st = SimpleTree('a', [SimpleTree('b', [SimpleTree('d'), SimpleTree('e')] ), SimpleTree('c', [SimpleTree('h'), SimpleTree('g')]) ])
+    print(st)
+
+
+if __name__ == '__main__':
+    main()
+
+