code: def test_base_outlier_detector_remove_na(data):
      """Tests `remove_na` method."""
      detect_outlier = BaseOutlierDetector()
      y = data["y_clean"].copy()
      y = pd.Series(y)
      y[5] = None
      y[70] = None
  
      y_na_removed = detect_outlier.remove_na(y)
  
      # Original length and new length.
      assert len(y) == 100
      assert len(y_na_removed) == 98
  
      y = pd.Series([None, None, None, 5, None])
      with pytest.raises(
          ValueError,
          match="Length of y after removing NAs is less than 2",
      ):
          detect_outlier.remove_na(y)
  
imports: import numpy
  import pandas
  import pytest
  from greykite.common.features.outlier import EXPONENTIAL_SMOOTHING
  from greykite.common.features.outlier import MOVING_MEDIAN
  from greykite.common.features.outlier import BaseOutlierDetector
  from greykite.common.features.outlier import DetectionResult
  from greykite.common.features.outlier import DiffMethod
  from greykite.common.features.outlier import TukeyOutlierDetector
  from greykite.common.features.outlier import ZScoreOutlierDetector
  from greykite.common.viz.timeseries_annotate import plot_lines_markers
label_desc: Use image node_id 7 for calling a global function with example usage: test_base_outlier_detector_remove_na(data) without return types