code: def test_missing_values_ratio(self):
      seriesF = TimeSeries.from_times_and_values(
          self.time, list(range(27)) + [np.nan] * 3
      )
  
      # univariate case
      assert missing_values_ratio(seriesF) == 0.1
  
      # multivariate case
      assert missing_values_ratio(seriesF.stack(seriesF)) == 0.1
  
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 7 for calling the TestMissingValues obj's underlying member method code with example usage: obj.test_missing_values_ratio() without return types