code: def test_get_feature_names_out_raises_when_input_features_is_string(
      df_time,
  ):
      tr = ExpandingWindowFeatures(functions=["mean", "sum"])
      tr.fit(df_time)
  
      with pytest.raises(ValueError):
          # get error when user does not pass a list
          tr.get_feature_names_out(input_features="ambient_temp")
  
file_path: feature_engine/tests/test_time_series/test_forecasting/test_expanding_window_features.py
imports: import numpy
  import pytest
  from pandas.testing import assert_frame_equal
  from feature_engine.timeseries.forecasting import ExpandingWindowFeatures
label_desc: Use image node_id 1 for calling a global function with example usage: test_get_feature_names_out_raises_when_input_features_is_string(df_time) without return types