nodes: 0, module; 1, function_definition; 2, function_name:children; 3, parameters; 4, block; 5, identifier:self; 6, expression_statement; 7, return_statement; 8, comment:"""
          The list of child messages and actions sorted by task level, excluding the
          start and end messages.
          """; 9, call; 10, identifier:pvector; 11, argument_list; 12, call; 13, identifier:sorted; 14, argument_list; 15, call; 16, keyword_argument; 17, attribute; 18, argument_list; 19, identifier:key; 20, lambda; 21, attribute; 22, identifier:values; 23, lambda_parameters; 24, attribute; 25, identifier:self; 26, identifier:_children; 27, identifier:m; 28, identifier:m; 29, identifier:task_level
code: def children(self):
          """
          The list of child messages and actions sorted by task level, excluding the
          start and end messages.
          """
          return pvector(
              sorted(self._children.values(), key=lambda m: m.task_level))