Get the underlying C reference from this object.

        :rtype: uamqp.c_uamqp.cProperties

def get_properties_obj(self):
        """Get the underlying C reference from this object.

        :rtype: uamqp.c_uamqp.cProperties
        """
        properties = c_uamqp.cProperties()
        self._set_attr('message_id', properties)
        self._set_attr('user_id', properties)
        self._set_attr('to', properties)
        self._set_attr('subject', properties)
        self._set_attr('reply_to', properties)
        self._set_attr('correlation_id', properties)
        self._set_attr('content_type', properties)
        self._set_attr('content_encoding', properties)
        self._set_attr('absolute_expiry_time', properties)
        self._set_attr('creation_time', properties)
        self._set_attr('group_id', properties)
        self._set_attr('group_sequence', properties)
        self._set_attr('reply_to_group_id', properties)
        return properties