export {
  Aggregate,
  Apply,
  AxisTicks,
  Bin,
  Collect,
  Compare,
  CountIndex,
  CountPattern,
  CrossFilter,
  DataJoin,
  Encode,
  Extent,
  Facet,
  Field,
  Filter,
  Fold,
  Force,
  Generate,
  GeoPath,
  GeoPoint,
  GeoShape,
  Graticule,
  Impute,
  LegendEntries,
  LinkPath,
  Lookup,
  MultiExtent,
  Nest,
  NoOp,
  Pack,
  Params,
  Partition,
  Pie,
  Projection,
  Range,
  Rank,
  Reflow,
  Relay,
  ResolveFilter,
  Sample,
  Scale,
  Sieve,
  Stack,
  Stratify,
  Subflow,
  Tree,
  TreeLinks,
  Treemap,
  TupleIndex,
  Values,
  Voronoi
} from 'vega-dataflow';

export {default as Bound} from './Bound';
export {default as ChartLayout} from './ChartLayout';
export {default as Mark} from './Mark';
export {default as Render} from './Render';

@@ -258,16 +258,23 @@
 Impute,%0A
+  Key,%0A
   Legend

Add Key operator.