code: def _list_outputs(self):
      global _set_len
      outputs = self._outputs().get()
      _set_len = outputs["output1"] = len(self.inputs.input1)
      return outputs
  
imports: import pytest
  from ....None import config
  from ...None import engine
  from ....interfaces import base
  from ....interfaces.utility import IdentityInterface, Function, Merge
  from ....interfaces.base import traits, File
label_desc: Use image node_id 2 for calling the SetInterface obj's underlying member method code with example usage: obj._list_outputs() and returns: outputs