anchor.diff:        for (component in iterate(result).by_class()){
           detach(spannerLib.Spanner, component);
         }
  -      if (result is Component){
  +      if (result is this.runtimeType){
           result = [result];
         }
         else {
           result = list(result);
         }
         result = selectionLib.Selection(result);
  -      return result
  +      return result;
     }
   
     _cache_named_children() {
  
positive.code: import 'package:abjad/selection.dart' as selectionLib;
  import 'package:abjad/timespan.dart' as timespanLib;
  import 'package:abjad/spanner' as spannerLib;
  import 'package:abjad/utilities.dart' show attach, set_, deatch, iterate, mutate, override;
  import 'abjad.abc.AjadOject' show AbjadObject;
  
  
  class Component extends AbjadObject{
  
negative.code:     return name_dictionary;
    }
  
    _copy_with_children_and_indicators_but_without_spanners(){
      return _copy_with_indicators_but_without_children_or_spanners();
    }
  
    _copy_with_indicators_but_without_children_or_spanners(){
      //@TODO: figure out how to translate python splat.
      var cpy = new this.runtimeType(*this.__getnewargs__());
      for (var indicator in _get_indicators()){
        var new_indicator = copy.copy(indicator);
        attach(new_indicator, cpy);
      }
      return cp;
    }
  
    /*
      def _detach_grace_containers(self, kind=None):
          from abjad.tools import scoretools
          grace_containers = self._get_grace_containers(kind=kind)
  