code: def test_CSZFillna(self):
      origin_df = D.features(
          D.instruments(market="csi300"),
          fields=["$high", "$open", "$low", "$close"],
      )
      origin_df = origin_df.groupby("datetime", group_keys=False).apply(
          lambda x: x[97:99]
      )[228:238]
      df = origin_df.copy()
      CSZFillna(fields_group=None).__call__(df)
      assert (
          ~df[1:2].isna().all().all()
          and origin_df[1:2].isna().all().all()
      )
  
file_path: qlib/tests/data_mid_layer_tests/test_processor.py
imports: import unittest
  import numpy
  from qlib.data import D
  from qlib.tests import TestAutoData
  from qlib.data.dataset.processor import MinMaxNorm, ZScoreNorm, CSZScoreNorm, CSZFillna
label_desc: Use image node_id 3 for calling the TestProcessor obj's underlying member method code with example usage: obj.test_CSZFillna() without return types