code: def test_dimensionality_reducer_placeholder_methods():
      reducer = MockReducer(None, None)
      with pytest.raises(NotImplementedError):
          reducer.reduce()
  
imports: import pytest
  from dowhy.data_transformer import DimensionalityReducer
label_desc: Use image node_id 1 for calling a global function with example usage: test_dimensionality_reducer_placeholder_methods() without return types