code: public function getSlots($first, $last)
      {
          if (!static::isValidRange($first, $last)) {
              throw new \OutOfBoundsException("Invalid slot range $first-$last");
          }
  
          return array_intersect_key($this->slots, array_fill($first, $last - $first + 1, null));
      }
docs: Returns the specified slot range.
  
  @param int $first Initial slot of the range.
  @param int $last  Last slot of the range.
  
  @return array