public function setCompletedAt($completed_at) {
        
        $this -> completed_at = $completed_at !== null ? new \DateTime($completed_at) : null;
        return $this;
    }
public function setCompletedAt($completed_at) {
        
        $this -> completed_at = $completed_at !== null ? new \DateTime($completed_at) : null;
        return $this;
    }
public function setCompletedAt ( $ completed_at ) { $ this -> completed_at = $ completed_at !== null ? new \ DateTime ( $ completed_at ) : null ; return $ this ; }
Sets the completed at
@param string $completed_at
@return TimestampAwareTrait
Sets the completed at