@classmethod
def release_api(cls, version, server, user, port, password, exp_id=None):
    """ Release an OMF API with this credentials

        :param version: OMF Version. Either 5 or 6
        :type version: str
        :param server: Xmpp Server Adress
        :type server: str
        :param user: Xmpp User
        :type user: str
        :param port: Xmpp Port (Default : 5222)
        :type port: str
        :param password: Xmpp Password
        :type password: str
        :param exp_id: Id of the experiment
        :type exp_id: str

        """
    if version and user and server and port and password:
        key = cls._make_key(version, server, user, port, password, exp_id)
        if key in cls._apis:
            cls._apis[key]['cnt'] -= 1
            if cls._apis[key]['cnt'] == 0:
                omf_api = cls._apis[key]['api']
                omf_api.disconnect()
                del cls._apis[key]
