def add_numbers(file: list, tel_numbers: set) -> set:
    """
    Given a file adds all available numbers into a set
    :param file: file containing telephone numbers
    :param tel_numbers: variable used to contain the telephone numbers
    :return: tel_numbers with file numbers extracted
    """
    for column in [0, 1]:
        temp_numbers = [data[column] for data in file]
        tel_numbers.update(temp_numbers)
    return tel_numbers