def value_to_bytes(self, obj, value, default_endianness=DEFAULT_ENDIANNESS):
return struct.pack(str(self.endianness or default_endianness) + self.struct_format, value)<EOL>
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