<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def length(self):
 """ Return the value length :rtype : int """

        if isinstance(self._value, int):
            return byte_len(self._value)
        if self._value is None:
            return 0
        return len(self._value)