code: def get_missing_df():
      data = np.random.random_sample((50, 5))
      mask = np.random.random_sample((50, 5))
      mask[mask >= 0.4] = 2
      mask[mask < 0.4] = 1
      mask[mask < 0.2] = 0
      data[mask == 0] = None
      data[mask == 1] = np.nan
      df = pd.DataFrame(data, columns=["a", "b", "c", "d", "e"])
      df["a"] = np.nan  # make sure column 'a' has are all N/A
      df["datetime"] = pd.date_range("1/1/2019", periods=50)
      return df
  
file_path: BigDL/python/chronos/test/bigdl/chronos/data/utils/test_quality_inspection.py
imports: import pytest
  import pandas
  import numpy
  from unittest import TestCase
  from bigdl.chronos.data.utils.quality_inspection import quality_check_timeseries_dataframe
  from ...None import op_torch, op_tf2
label_desc: Use image node_id 1 for calling a global function with example usage: get_missing_df() and returns: df