code: public function seek($position)
      {
          if (!array_key_exists($position, $this->elements)) {
              throw new \InvalidArgumentException(
                  sprintf('Position %s does not exist in collection', $position)
              );
          }
  
          reset($this->elements);
  
          while (key($this->elements) !== $position) {
              next($this->elements);
          }
      }
docs: Seek to a position within the collection
  
  @param $position
  @return void