import warnings


def convert_method_3_nb_into_str(method_3_nb):
    """
    Converts method_3_nb into string

    Parameters
    ----------
    method_3_nb : int
        Number of method 3

    Returns
    -------
    method_3_str : str
        String of method 3
    """
    if method_3_nb is None:
        msg = 'method_3_nb is None. Going to return None.'
        warnings.warn(msg)
        return None

    dict_method_3 = {0: 'food_pro',
                     1: 'metal',
                     2: 'rest',
                     3: 'sports',
                     4: 'repair'}

    method_3_str = dict_method_3[method_3_nb]

    return method_3_str