def get_features_from_df(df, features):
    """
    Helper function to get feature columns of a dataframe.

    Args:
        df (pd.DataFrame)       A pd.DataFrame where the features are extracted.
        features (list of str)  Name of the features columns in df.

    Returns:
            feature_df      A pd.DataFrame that only contains the features used in ML.
    """
    feature_df = df[features]
    return feature_df