nodes: 0, module; 1, function_definition; 2, function_name:sort; 3, parameters; 4, block; 5, identifier:self; 6, default_parameter; 7, expression_statement; 8, expression_statement; 9, if_statement; 10, identifier:callback; 11, None; 12, comment:"""
          Sort through each item with a callback.
  
          :param callback: The callback
          :type callback: callable or None
  
          :rtype: Collection
          """; 13, assignment; 14, identifier:callback; 15, block; 16, else_clause; 17, identifier:items; 18, attribute; 19, return_statement; 20, block; 21, identifier:self; 22, identifier:items; 23, call; 24, return_statement; 25, attribute; 26, argument_list; 27, call; 28, identifier:self; 29, identifier:__class__; 30, call; 31, attribute; 32, argument_list; 33, identifier:sorted; 34, argument_list; 35, identifier:self; 36, identifier:__class__; 37, call; 38, identifier:items; 39, keyword_argument; 40, identifier:sorted; 41, argument_list; 42, identifier:key; 43, identifier:callback; 44, identifier:items
code: def sort(self, callback=None):
          """
          Sort through each item with a callback.
  
          :param callback: The callback
          :type callback: callable or None
  
          :rtype: Collection
          """
          items = self.items
  
          if callback:
              return self.__class__(sorted(items, key=callback))
          else:
              return self.__class__(sorted(items))