Creates a selector expression of the offset.

        :rtype: bytes

def selector(self):
        """
        Creates a selector expression of the offset.

        :rtype: bytes
        """
        operator = ">=" if self.inclusive else ">"
        if isinstance(self.value, datetime.datetime):
            timestamp = (calendar.timegm(self.value.utctimetuple()) * 1000) + (self.value.microsecond/1000)
            return ("amqp.annotation.x-opt-enqueued-time {} '{}'".format(operator, int(timestamp))).encode('utf-8')
        if isinstance(self.value, six.integer_types):
            return ("amqp.annotation.x-opt-sequence-number {} '{}'".format(operator, self.value)).encode('utf-8')
        return ("amqp.annotation.x-opt-offset {} '{}'".format(operator, self.value)).encode('utf-8')