The type of the toc item. Well-known types are:
layer
@arcgis/core/layer/Layer
sublayer
wms
map-image
root
The type of the toc item. Well-known types are:
layer- item represents an layer (in the sense of a@arcgis/core/layer/Layerinstance)sublayer- item represents a sub layer (e.g.wmsormap-imagesublayer)root- item is the root of the layer tree The list may be extended in the future.