Sample Proto

class Constants():

        AUTH_DATA = b'\x00\x00'
        INIT_STRING_DATA = b'\x00\x01'
        MIXED_DATA = b'\x00\x02'
        LEVEL_DATA = b'\x00\x03'
        DATA_REFUSED = b'\x00\x04'
        DATA_FINISH = b'\x00\x05'
        DATA_XML = b'\x00\x06'

        PS_HALF = b'\x00\x00'
        PS_NORMAL = b'\x00\x01'
        PS_DOUBLE = b'\x00\x02'
        PS_REALTIME = b'\x00\x03'

        VERSION_BINARY = b'\x00\x00'
        VERSION_XML = b'\x00\x01'

		CMD_MSL_LNCH_SEQ_1 = b'\x00\x00'
		CMD_MSL_LNCH_SEQ_2 = b'\x00\x01'
		CMD_MSL_LNCH_SEQ_3 = b'\x00\x02'
		CMD_MSL_LNCH_SEQ_4 = b'\x00\x03'
		CMD_MSL_LNCH_SEQ_5 = b'\x00\x04'

		CMD_CRD_INP_LAT = b'\x00\x05'
		CMD_CRD_INP_LNG = b'\x00\x06'




    class Header(dict):
        fields = {
            "key_hash":    bitarray.bitarray(32),  # asByte & 32
            "cc_id":       bitarray.bitarray(32),  # asByte & 32
            "msl_id":      bitarray.bitarray(32),  # asByte & 32
            "data_type":   bitarray.bitarray(16),  # asByte & 16
            "id":          bitarray.bitarray(16),  # asByte & 16
            "packet_len":  bitarray.bitarray(16),  # asByte & 16
            "proto_speed": bitarray.bitarray(4),   # asByte & 4
            "header_len":  bitarray.bitarray(4),   # asByte & 4
            "version":     bitarray.bitarray(8)    # asByte & 8
        }

        def __init__(self):
            super().__init__()
            for f in self.fields.values():
                f.setall(False)

        def pack(self):
            packed_header = bitarray.bitarray(endian='little')
            for f in self.fields.values():
                packed_header.append(f)
            return packed_header.tobytes()