Function isGroupLayerExtension

isGroupLayerExtension(extension): extension is GroupLayerExtension<LayerExtensionProperties, LayerExtension<LayerExtensionProperties>, GroupLayerExtensionCollection<LayerExtensionProperties, LayerExtension<LayerExtensionProperties>>>
Returns true if the extension is a GroupLayerExtension.
Parameters
- extension: unknown
  The extension to check.
Returns extension is GroupLayerExtension<LayerExtensionProperties, LayerExtension<LayerExtensionProperties>, GroupLayerExtensionCollection<LayerExtensionProperties, LayerExtension<LayerExtensionProperties>>>