add
@NonNull()
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Adds a new [style layer](https://docs.mapbox.com/mapbox-gl-js/style-spec/#layers). Whenever a new style is being parsed and currently used style has persistent layers, an engine will try to do following: - keep the persistent layer at its relative position - keep the source used by a persistent layer - keep images added through `addStyleImage` method In cases when a new style has the same layer, source or image resource, style's resources would be used instead and `MapLoadingError` event will be emitted.
Return
string describing an error if the operation was not successful, or empty otherwise.
Parameters
layerPosition
If not empty, the new layer will be positioned according to `layer position` parameters.
properties
A map of style layer properties.