code: def test_diff_methods_init():
      """Tests the dataclass DiffMethod."""
      baseline_method = DiffMethod()
  
      assert baseline_method.name is None
      assert baseline_method.param is not None
  
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 4 for calling a global function with example usage: test_diff_methods_init() without return types