code: def test_mapper_with_timestamp(self):
      test_cases = [
          (self.lin_series, self.zeroes),
          (
              [self.lin_series, self.lin_series],
              [self.zeroes, self.zeroes],
          ),
      ]
  
      for to_transform, expected_output in test_cases:
          transformed = self.subtract_month.transform(to_transform)
          if isinstance(to_transform, list):
              expected_output = [
                  o.with_columns_renamed(
                      o.components[0], t.components[0]
                  )
                  for t, o in zip(transformed, expected_output)
              ]
          else:
              expected_output = expected_output.with_columns_renamed(
                  expected_output.components[0],
                  transformed.components[0],
              )
          assert transformed == expected_output
  
file_path: darts/darts/tests/dataprocessing/transformers/test_mappers.py
imports: import numpy
  import pandas
  from darts import TimeSeries
  from darts.dataprocessing.transformers.mappers import InvertibleMapper, Mapper
  from darts.utils.timeseries_generation import constant_timeseries, linear_timeseries
label_desc: Use image node_id 7 for calling the TestMappers obj's underlying member method code with example usage: obj.test_mapper_with_timestamp() without return types