/**
  * Populates the sprints array
  *
  * @return void
  */
 protected function _populateSprints()
 {
     if ($this->_sprints === null) {
         $this->_sprints = array();
         foreach (TBGMilestone::getSprintsByProjectID($this->getID()) as $sprint) {
             $this->_sprints[$sprint->getID()] = $sprint;
         }
     }
 }