code: public function channelGroupClientList($cgid = null, $cid = null, $cldbid = null)
      {
          if ($this["virtualserver_default_channel_group"] == $cgid) {
              return array();
          }
  
          return $this->execute(
              "channelgroupclientlist",
              array("cgid" => $cgid, "cid" => $cid, "cldbid" => $cldbid)
          )->toArray();
      }
docs: Returns all the client and/or channel IDs currently assigned to channel groups. All three
  parameters are optional so you're free to choose the most suitable combination for your
  requirements.
  
  @param  integer $cgid
  @param  integer $cid
  @param  integer $cldbid
  @return array