code: def test_fill_const_series_with_const_value(self):
      const_transformer = MissingValuesFiller(fill=2.0)
      transformed = const_transformer.transform(
          self.const_series_with_holes
      )
      assert self.const_series == transformed
  
file_path: darts/darts/tests/dataprocessing/transformers/test_missing_values_filler.py
imports: import numpy
  import pandas
  from darts.dataprocessing.transformers import MissingValuesFiller
  from darts.timeseries import TimeSeries
label_desc: Use image node_id 1 for calling the TestMissingValuesFiller obj's underlying member method code with example usage: obj.test_fill_const_series_with_const_value() without return types