This defaults to
labelLocation, and indicates the name of a property whose value can be expected to hold the location at which the label overlay should be located. The default value for this is
labelLocation, but the key here is that the Toolkit looks in the edge data for
labelLocation, so the location is dynamic, and can be changed by updating
labelLocation. This parameter allows you to change the name of the property that the Toolkit will look for in the edge data.