The feature the title function receives.
Optionaltitle?: ((feature: F) => string) | DataDrivenPropertyValueSpecification<string>Text content for the label.
A function is called once per feature when it is shown, and its result is drawn as given. A MapLibre expression is evaluated per feature by the layer, over the properties the feature is drawn with, and replaces the module's whole label text.
A LabelConfig that also sets what the label says, for the labels a module writes beside the features it shows.