Each section below is a separate representation of the same visualization IR.
All four parse to the same in-memory object, exercised by
round-trip-representations.test.js. The HTML form here is the
cut-1 author surface; JSON, YAML, and Turtle are data-exchange forms.
The <slc-chart> tree is parsed by parseIntermediateRepresentation.
Round-trips through renderJsonIntermediateRepresentation and parseJsonIntermediateRepresentation.
Round-trips through renderYamlIntermediateRepresentation and parseYamlIntermediateRepresentation.
Round-trips through renderTurtleIntermediateRepresentation and parseTurtleIntermediateRepresentation.