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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def create_function_from_request_pdu(pdu):
 """ Return function instance, based on request PDU. :param pdu: Array of bytes. :return: Instance of a function. """

    function_code = get_function_code_from_request_pdu(pdu)
    try:
        function_class = function_code_to_function_map[function_code]
    except KeyError:
        raise IllegalFunctionError(function_code)

    return function_class.create_from_request_pdu(pdu)