class_docstr: Add operator that can take in undefined amount of inputs and saves results to '<input_name>_sum'
  column of result dataframe.
code: def __call__(self, **kwargs):
      cols = []
      ret = []
      for key, value in kwargs.items():
          cols.append((key + "_sum", type(value)))
          ret.append(value + self._factor)
  
      outputs = NamedTuple("Outputs", cols)
      return outputs(*ret)
  
imports: from typing import NamedTuple
  from towhee.operator import Operator, SharedType
label_desc: Use image node_id 2 for calling the AddOperatorV2 obj's underlying member method code with example usage: obj.__call__() and returns: outputs