public function addPeer($label, CachePeer $peer, $mountPoint)
 {
     Assert::isLesserOrEqual($mountPoint, $this->summaryWeight);
     Assert::isGreaterOrEqual($mountPoint, 0);
     $this->doAddPeer($label, $peer);
     $this->peers[$label]['mountPoint'] = $mountPoint;
     $this->sorted = false;
     return $this;
 }