old_contents: """A more or less complete user-defined wrapper around dictionary objects."""
  
  class UserDict:
      def __init__(self, dict=None):
          self.data = {}
          if dict is not None: self.update(dict)
      def __repr__(self): return repr(self.data)
      def __cmp__(self, dict):
          if isinstance(dict, UserDict):
              return cmp(self.data, dict.data)
          else:
              return cmp(self.data, dict)
      def __len__(self): return len(self.data)
      def __getitem__(self, key): return self.data[key]
      def __setitem__(self, key, item): self.data[key] = item
      def __delitem__(self, key): del self.data[key]
      def clear(self): self.data.clear()
      def copy(self):
          if self.__class__ is UserDict:
              return UserDict(self.data)
          import copy
          data = self.data
          try:
              self.data = {}
              c = copy.copy(self)
          finally:
              self.data = data
          c.update(self)
          return c
      def keys(self): return self.data.keys()
      def items(self): return self.data.items()
      def iteritems(self): return self.data.iteritems()
      def iterkeys(self): return self.data.iterkeys()
      def itervalues(self): return self.data.itervalues()
      def values(self): return self.data.values()
      def has_key(self, key): return self.data.has_key(key)
      def update(self, dict):
          if isinstance(dict, UserDict):
              self.data.update(dict.data)
          elif isinstance(dict, type(self.data)):
              self.data.update(dict)
          else:
              for k, v in dict.items():
                  self[k] = v
      def get(self, key, failobj=None):
          if not self.has_key(key):
              return failobj
          return self[key]
      def setdefault(self, key, failobj=None):
          if not self.has_key(key):
              self[key] = failobj
          return self[key]
      def popitem(self):
          return self.data.popitem()
      def __contains__(self, key):
          return key in self.data
  
  class IterableUserDict(UserDict):
      def __iter__(self):
          return iter(self.data)
  
new_contents: """A more or less complete user-defined wrapper around dictionary objects."""
  
  class UserDict:
      def __init__(self, dict=None):
          self.data = {}
          if dict is not None: self.update(dict)
      def __repr__(self): return repr(self.data)
      def __cmp__(self, dict):
          if isinstance(dict, UserDict):
              return cmp(self.data, dict.data)
          else:
              return cmp(self.data, dict)
      def __len__(self): return len(self.data)
      def __getitem__(self, key): return self.data[key]
      def __setitem__(self, key, item): self.data[key] = item
      def __delitem__(self, key): del self.data[key]
      def clear(self): self.data.clear()
      def copy(self):
          if self.__class__ is UserDict:
              return UserDict(self.data)
          import copy
          data = self.data
          try:
              self.data = {}
              c = copy.copy(self)
          finally:
              self.data = data
          c.update(self)
          return c
      def keys(self): return self.data.keys()
      def items(self): return self.data.items()
      def iteritems(self): return self.data.iteritems()
      def iterkeys(self): return self.data.iterkeys()
      def itervalues(self): return self.data.itervalues()
      def values(self): return self.data.values()
      def has_key(self, key): return self.data.has_key(key)
      def update(self, dict):
          if isinstance(dict, UserDict):
              self.data.update(dict.data)
          elif isinstance(dict, type(self.data)):
              self.data.update(dict)
          else:
              for k, v in dict.items():
                  self[k] = v
      def get(self, key, failobj=None):
          if not self.has_key(key):
              return failobj
          return self[key]
      def setdefault(self, key, failobj=None):
          if not self.has_key(key):
              self[key] = failobj
          return self[key]
      def pop(self, key):
          return self.data.pop(key)
      def popitem(self):
          return self.data.popitem()
      def __contains__(self, key):
          return key in self.data
  
  class IterableUserDict(UserDict):
      def __iter__(self):
          return iter(self.data)
  
subject: Add pop() to UserDict.