code: def test_error_if_input_df_contains_na_in_transform(
      df_vartypes, df_na
  ):
      # test case 4: when dataset contains na, transform method
      with pytest.raises(ValueError):
          transformer = EqualFrequencyDiscretiser()
          transformer.fit(df_vartypes)
          transformer.transform(
              df_na[["Name", "City", "Age", "Marks", "dob"]]
          )
  
file_path: feature_engine/tests/test_discretisation/test_equal_frequency_discretiser.py
imports: import pandas
  import pytest
  from sklearn.exceptions import NotFittedError
  from feature_engine.discretisation import EqualFrequencyDiscretiser
label_desc: Use image node_id 6 for calling a global function with example usage: test_error_if_input_df_contains_na_in_transform(df_vartypes, df_na) without return types