roots property
Gets or sets the collection of root vertexes.
Initially this will be an empty Set.
If the #path is either TreeLayout.PathDestination|PathDestination or TreeLayout.PathSource|PathSource, this layout can easily determine all of the tree roots by searching the whole network. Otherwise, you should explicitly initialize this collection with one or more TreeVertexes.
Implementation
_i3.Set<_i2.Object> get roots => _i4.getProperty(
this,
'roots',
);