def _add_missing_parameters(flattened_params_dict):
    """Add the standard etl parameters if they are missing."""
    standard_params = ['ferc1_years',
                       'eia923_years',
                       'eia860_years',
                       'epacems_years',
                       'epacems_states']
    for param in standard_params:
        try:
            _ = flattened_params_dict[param]
        except KeyError:
            flattened_params_dict[param] = []
    return flattened_params_dict