anchor.diff:      Tuple slice([$dart$core.int index]) => List.$slice(this, index);
       List initial([$dart$core.int length]) => List.$initial(this, length);
       List terminal([$dart$core.int length]) => List.$terminal(this, length);
  -    List span([Integer from, Integer to]) => List.$span(this, from, to);
  -    List spanFrom([Integer from]) => List.$spanFrom(this, from);
  -    List spanTo([Integer to]) => List.$spanTo(this, to);
  -    List measure([Integer from, $dart$core.int length]) => List.$measure(this, from, length);
       Sequential collect([Callable collecting]) => List.$collect(this, collecting);
       List mapElements([Callable mapping]) => List.$mapElements(this, mapping);
       $dart$core.bool get empty => Collection.$get$empty(this);
  +    $dart$core.String toString() => Collection.$get$string(this);
       Iterable get permutations => Collection.$get$permutations(this);
       Sequential sequence() => Iterable.$sequence(this);
       $dart$core.Object indexes() => Iterable.$indexes(this);
  
positive.code:     Sequential collect([Callable collecting]) => List.$collect(this, collecting);
      List mapElements([Callable mapping]) => List.$mapElements(this, mapping);
      $dart$core.bool get empty => Collection.$get$empty(this);
      Iterable get permutations => Collection.$get$permutations(this);
      Sequential sequence() => Iterable.$sequence(this);
      $dart$core.Object indexes() => Iterable.$indexes(this);
  
negative.code:         }
          return result;
      }
      $dart$core.bool get empty => Sequence.$get$empty(this);
      Range get keys => Sequence.$get$keys(this);
      Range indexes() => Sequence.$indexes(this);
  