def _stops_definitions(df):
    """
    Append GTFS definitions for stop columns to stop dataframe

    Parameters
    ----------
    df : pandas:DataFrame
        stops dataframe

    Returns
    -------
    df : pandas.DataFrame
    """
    if 'location_type' in df.columns:
        stops_location_type = {(0): 'stop', (1): 'station', (2):
            'station entrance'}
        df['location_type_desc'] = df['location_type'].map(stops_location_type
            .get)
    if 'wheelchair_boarding' in df.columns:
        stops_wheelchair_boardings = {(0):
            'No accessibility information available for the stop', (1):
            'At least some vehicles at this stop can be boarded by a rider in a wheelchair'
            , (2): 'Wheelchair boarding is not possible at this stop'}
        df['wheelchair_boarding_desc'] = df['wheelchair_boarding'].map(
            stops_wheelchair_boardings.get)
    return df
