Create bytes from properties

def to_bytes(self):
        '''
        Create bytes from properties
        '''
        # Verify that properties make sense
        self.sanitize()

        # Start with the type
        bitstream = BitArray('uint:4=%d' % self.message_type)

        # Add padding
        bitstream += self._reserved1

        # Add the record count
        bitstream += BitArray('uint:8=%d' % len(self.records))

        # Add the nonce
        bitstream += BitArray(bytes=self.nonce)

        # Add the records
        for record in self.records:
            bitstream += record.to_bitstream()

        return bitstream.bytes