code: public function expiresAt($expires)
      {
          if ($expires instanceof DateTimeInterface) {
              $this->expires = $expires;
          } else {
              $this->expires = null;
          }
          
          return $this;
      }
docs: Sets the expiration time for this cache item.
  
  @param \DateTimeInterface $expires
  The point in time after which the item MUST be considered expired.
  If null is passed explicitly, a default value MAY be used. If none is set,
  the value should be stored permanently or for as long as the
  implementation allows.
  
  @return static The called object.