docs: function(jidOrUserId, callback) {
  
          /**
           * Callback for QB.chat.roster.add(). Run without parameters.
           * @callback addRosterCallback
           * */
          var self = this;
          var userJid = this.helpers.jidOrUserId(jidOrUserId);
          var userId = this.helpers.getIdFromNode(userJid).toString();
  
          self.contacts[userId] = {
              subscription: 'none',
              ask: 'subscribe'
          };
  
          self._sendSubscriptionPresence({
              jid: userJid,
              type: 'subscribe'
          });
  
          if (typeof callback === 'function') {
              callback();
          }
      }