old_contents: # Copyright (c) 2017 The Regents of the University of Michigan.
  # All Rights Reserved. Licensed according to the terms of the Revised
  # BSD License. See LICENSE.txt for details.
  
  class MutableTree:
  
      def __init__ (self, value = None):
          self.child = None
          self.children = [ ]
          self.value = value
  
      @property
      def value (self):
          return self.__value
  
      @value.setter
      def value (self, x):
          self.__value = x
  
      def __len__ (self):
          return len(self.children)
  
      def full_length (self):
          return len(self)
  
      def __iter__ (self):
          return iter(self.children)
  
      def walk (self):
          return iter(self)
  
      def __getitem__ (self, index):
          return self.children[index]
  
      def insert (self, index, node):
          self.child = node
          self.children.insert(index, node)
  
      def __repr__ (self):
          debug = self.__class__.__name__
  
          if self.value is not None:
              debug += " " + repr(self.value)
  
          return "<{} {}>".format(debug, repr(self.children))
  
new_contents: # Copyright (c) 2017 The Regents of the University of Michigan.
  # All Rights Reserved. Licensed according to the terms of the Revised
  # BSD License. See LICENSE.txt for details.
  
  class MutableTree:
  
      def __init__ (self, value = None):
          self.children = [ ]
          self.value = value
  
      @property
      def value (self):
          return self.__value
  
      @value.setter
      def value (self, x):
          self.__value = x
  
      def __len__ (self):
          return len(self.children)
  
      def full_length (self):
          return len(self)
  
      def __iter__ (self):
          return iter(self.children)
  
      def walk (self):
          return iter(self)
  
      def __getitem__ (self, index):
          return self.children[index]
  
      def insert (self, index, node):
          self.children.insert(index, node)
  
      def __repr__ (self):
          debug = self.__class__.__name__
  
          if self.value is not None:
              debug += " " + repr(self.value)
  
          return "<{} {}>".format(debug, repr(self.children))
  
subject: Remove unused MutableTree.child