Using 'groups' in call to graph_tool.draw.sfdp_layout()


I have been unable to see any effect on the layout when using the 'groups'

For example, I have tried setting groups equal to a VertexPropertyMap as

        vprop_layout_groups = self.new_vertex_property("int") # Vertex

With layout_groups = [0 0 0 0 0 0 1 1 1]
I can see no grouping effect on the positions of the vertices as returned by
The three vertices without edges are in the '1' group. The connected
vertices are in the '0' group.
I have been unable to find any example showing a call to sfdp_layout() where
'groups' is used.
Is there a working example available?

Thank you.

p.s. Is there a way to donate money to the graph-tool project?

You should experiment with the `gamma` parameter which controls the
strength of the attractive force between nodes of the same group.