code: def test_bfill(self):
      seriesC: TimeSeries = TimeSeries.from_times_and_values(
          self.time, np.array([np.nan] * 10 + self.lin[-20:])
      )
  
      # Check that auto-backfill works properly
      assert self.series3 == fill_missing_values(seriesC, "auto")
  
file_path: darts/darts/tests/utils/test_missing_values.py
imports: import numpy
  import pandas
  from darts import TimeSeries
  from darts.utils.missing_values import fill_missing_values, missing_values_ratio
label_desc: Use image node_id 3 for calling the TestMissingValues obj's underlying member method code with example usage: obj.test_bfill() without return types