def finalize_substation_types(df_all_substations):
    """
    Specify bus_id and voltage columns as integer
    """

    # make float to integer
    df_all_substations["bus_id"] = df_all_substations["bus_id"].astype(int)
    df_all_substations.loc[:,
                           "voltage"] = df_all_substations["voltage"].astype(
                               int)

    return df_all_substations