class_docstr: Flat input list.
code: def __call__(self, inputs: List[NamedTuple("input", [("num", int)])]):
      Outputs = NamedTuple("Outputs", [("sum", int)])
      nums = [item.num for item in inputs]
      output = Outputs(sum(nums))
      return [output, output]
  
file_path: towhee/tests/unittests/mock_operators/sum_operator/sum_operator.py
imports: from typing import NamedTuple, List
  from towhee.operator import Operator, SharedType
label_desc: Use image node_id 2 for calling the SumOperator obj's underlying member method code with example usage: obj.__call__(inputs) and returns: list