code: def transform_b(self, data_input):
      return ["b"]
  
imports: import pytest
  from neuraxle.base import BaseStep
  from neuraxle.base import ExecutionContext
  from neuraxle.base import Identity, NonFittableMixin
  from neuraxle.data_container import DataContainer
  from neuraxle.hyperparams.space import HyperparameterSamples
  from neuraxle.pipeline import Pipeline
  from neuraxle.steps.flow import OptionalStep
  from neuraxle.steps.numpy import MultiplyByN
  from neuraxle.steps.output_handlers import OutputTransformerWrapper
label_desc: Use image node_id 4 for calling the Mutating2TransformsStep obj's underlying member method code with example usage: obj.transform_b(data_input) and returns: list