The four column names a choropleth declaration renames a region's facts to.
Narrowed to plain strings here so that extractor.ts — which reads what
amCharts drew — never has to know what a declaration is. A slot the author
left out stays undefined, and the extractor then walks its own chain for
that fact rather than treating the omission as a name.
Exported because the highlight path needs the same four: they decide which
regions the layer kept, and a resolver filtering by a different rule would
index a list of a different length.
The four column names a choropleth declaration renames a region's facts to.
Narrowed to plain strings here so that
extractor.ts— which reads what amCharts drew — never has to know what a declaration is. A slot the author left out staysundefined, and the extractor then walks its own chain for that fact rather than treating the omission as a name.Exported because the highlight path needs the same four: they decide which regions the layer kept, and a resolver filtering by a different rule would index a list of a different length.