def METHOD_NAME(self):
    """
    Finite state transducer for classifying serial.
        The serial is a combination of digits, letters and dashes, e.g.:
        c325-b -> tokens { cardinal { integer: "си три два пять би" } }
    """
    num_graph = self.single_digits_graph
    alpha = TO_CYRILLIC | RU_ALPHA
    delimiter = insert_space | pynini.cross("-", " ") | pynini.cross("/", " ")
    letter_num = pynini.closure(alpha + delimiter, 1) + num_graph
    num_letter = pynini.closure(num_graph + delimiter, 1) + alpha
    num_delimiter_num = pynini.closure(num_graph + delimiter, 1) + num_graph
    next_alpha_or_num = pynini.closure(delimiter + (alpha | num_graph))
    serial_graph = (letter_num | num_letter | num_delimiter_num) + next_alpha_or_num
    # at least 1 alpha and 1 digit is present
    at_least_one_alpha_num = (
        DAMO_SIGMA + (RU_ALPHA | pynini.project(TO_CYRILLIC, "input")) + DAMO_SIGMA + DAMO_DIGIT + DAMO_SIGMA
    ) | (DAMO_SIGMA + DAMO_DIGIT + DAMO_SIGMA + (RU_ALPHA | pynini.project(TO_CYRILLIC, "input")) + DAMO_SIGMA)
    serial_graph = pynini.compose(at_least_one_alpha_num, serial_graph.optimize()).optimize()
    # numbers only with 2+ delimiters
    serial_graph |= (
        num_graph + delimiter + num_graph + delimiter + num_graph + pynini.closure(delimiter + num_graph)
    ).optimize()
    return serial_graph.optimize()