Pinq\Iterators\Standard\IIterator::fetch PHP Метод

    public function fetch();

 protected function doFetch()
 {
     while ((list($innerKey, $innerValue) = $this->innerValuesIterator->fetch()) === null) {
         if ((list($this->outerKey, $this->outerValue) = $this->outerIterator->fetch()) === null) {
             return null;
         }
         $this->innerValuesIterator = $this->getInnerValuesIterator($this->outerKey, $this->outerValue);
         $this->innerValuesIterator->rewind();
     }
     $projectionFunction = $this->projectionFunction;
     return [$this->count++, $projectionFunction($this->outerValue, $innerValue, $this->outerKey, $innerKey)];
 }