code: private function getLineBreakCount(Tokens $tokens, $whiteStart, $whiteEnd)
      {
          $lineCount = 0;
          for ($i = $whiteStart; $i < $whiteEnd; ++$i) {
              $lineCount += Preg::matchAll('/\R/u', $tokens[$i]->getContent(), $matches);
          }
  
          return $lineCount;
      }
docs: @param Tokens $tokens
  @param int    $whiteStart
  @param int    $whiteEnd
  
  @return int