<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def value(self):
 """Return sub type and sub value as binary data. Returns: :class:`~pyof.foundation.basic_types.BinaryData`: BinaryData calculated. """

        binary = UBInt8(self.sub_type).pack() + self.sub_value.pack()
        return BinaryData(binary)