code: def test_ratio(self):
      tau = sample_tau(100000, ratio=0.4)
      sample = np.array(tau)
      before = np.sum(sample <= 1 / 0.3)
      beyond = np.sum(sample > 1 / 0.3)
      self.assertTrue(
          abs(0.4 - float(before) / (before + beyond)) < 0.006
      )
  
imports: import unittest
  import dask.dataframe
  import numpy
  import pandas
  from tsfresh import extract_features, extract_relevant_features
  from tsfresh.examples.driftbif_simulation import load_driftbif, sample_tau, velocity
  from tsfresh.feature_extraction import MinimalFCParameters
label_desc: Use image node_id 3 for calling the SampleTauTestCase obj's underlying member method code with example usage: obj.test_ratio() without return types