pipeline_steps.append(node(merging_features_to_main_data, inputs = dict(main_df = 'main_df', feature_1_df = 'feature_df1', feature_2_df = 'feature_df2'),
                                                                           outputs='main_feature_df'))

This is one pipeline, merging 2 feature_df into main_df. but what if I dont know how many feature_dfs in advance, how can I do that?