The type of this property.
A PropertyType enumerated value; read/write. One of:
PropertyType.PROPERTY A single property such as position or zoom.
PropertyType.INDEXED_GROUP A property group whose members have an editable name and an index. Effects and masks are indexed groups. For example, the masks property of a layer refers to a variable number of individual masks by index number.
PropertyType.NAMED_GROUPA property group in which the member names are not editable. Layers are named groups.