Whether the current endian is big endian.

def _is_big_endian(self):
        """
        Whether the current endian is big endian.
        """
        if self.endian == DataTypeMixIn.ENDIAN_NATIVE:
            return SYSTEM_ENDIAN == DataTypeMixIn.ENDIAN_BIG

        return self.endian in (DataTypeMixIn.ENDIAN_BIG, DataTypeMixIn.ENDIAN_NETWORK)