original_string: public function reduce(Callable $f, $initial = null) {
          return array_reduce($this->items, $f, $initial);
      }
code: public function reduce(Callable $f, $initial = null) {
          return array_reduce($this->items, $f, $initial);
      }
code_tokens: public function reduce ( Callable $ f , $ initial = null ) { return array_reduce ( $ this -> items , $ f , $ initial ) ; }
docstring: return a single value reduced from the collection by the
  provided function.
  
  @param callable $f
  @param null $initial
  @return mixed
docstring_tokens: return a single value reduced from the collection by the provided function .