A Vega-Lite top-level specification. This is the root class for all Vega-Lite specifications. (The json schema is generated from this type.)
This object must match the following conditions:
anyOf [TopLevelUnitSpec, TopLevelFacetSpec, TopLevelLayerSpec, anyOf [object, object], TopLevelConcatSpec, TopLevelVConcatSpec, TopLevelHConcatSpec]