return '[{}]'.format(','.join(array_attr_elts))
  raise NotImplementedError(
      'Proto AttrValue not recognized. type: {}, value: {}'.format(
          attr_type, attr_val))


def _collect_derived_attrs_from_proto(op_def):
  derived_attrs = set()
  for arg in op_def.input_arg:
    if arg.type_attr:
      derived_attrs.add(arg.type_attr)
    if arg.number_attr:
      derived_attrs.add(arg.number_attr)