code: public static function all(Iterator $iterator, callable $predicate) : bool
      {
          while ($iterator->valid()) {
              if (!Predicates::call($predicate, $iterator->current())) {
                  return false;
              }
              $iterator->next();
          }
          return true;
      }
docs: Returns true if every element returned by iterator satisfies the given predicate.
  If iterator is empty, true is returned.
  
  @param Iterator $iterator
  @param callable $predicate
  @return boolean