M method
Implementation
MfuncTuple M(Uint8List candidbytes, CandidBytes_i start_i) {
// get BigInt/int of the candid_nat64
String nat64_asabitstring = bytes_as_the_bitstring(Uint8List.fromList(candidbytes.sublist(start_i, start_i + 8).reversed.toList()));
BigInt va = BigInt.parse(nat64_asabitstring, radix: 2);
MfuncTuple m_func_tuple = MfuncTuple(Nat64(va), start_i+8);
return m_func_tuple;
}