The feature fn receives.
imageID - fn returns the id of an image in the style's sprite, or of one the module adds.poiCategory - fn returns a POI category, drawn with the SDK's icon for it, so data
that is not a search result can still look like one. On a places module, a
PlaceIconConfig.categoryIcons entry that matches the category draws instead.If fn returns undefined, that feature keeps the icon it has without a mapping.
Picks the icon of each feature a module draws, from the feature itself.