code: def value_to_bytes(self, obj, value, default_endianness=DEFAULT_ENDIANNESS):
          
          return struct.pack(str(self.endianness or default_endianness) + self.struct_format, value)
docs: Converts the given value to an appropriately encoded string of bytes that represents it.
  
          :param obj: The parent :class:`.PebblePacket` of this field
          :type obj: .PebblePacket
          :param value: The python value to serialise.
          :param default_endianness: The default endianness of the value. Used if ``endianness`` was not passed to the
                                     :class:`Field` constructor.
          :type default_endianness: str
          :return: The serialised value
          :rtype: bytes