code: def build_merged_df(df_names, group, original_dfs):
      keys = [f"{_}_{group}" for _ in df_names]
      return pd.concat([original_dfs[_] for _ in keys], keys=keys)
  
file_path: hyperparameter_hunter/tests/test_feature_engineering.py
imports: from hyperparameter_hunter.feature_engineering import merge_dfs, split_merged_df
  from hyperparameter_hunter.feature_engineering import DatasetNameReport, validate_dataset_names
  from hyperparameter_hunter.feature_engineering import get_engineering_step_params
  import pandas
  import pytest
label_desc: Use image node_id 1 for calling a global function with example usage: build_merged_df(df_names, group, original_dfs) and returns: pd