[graph-tool] GraphView and subclasses of Graph

Hi! Thanks for graph-tools, it looks like a fab project! I am toying around with a particular class of graphs for which I wrote a subclass of `graph_tools.Graph`. It should be great to be able to use `GraphView` for filtering (I'm implementing a divide-and-conquer algorithm and want to recur on subgraphs), but it seems that those will always behave as `Graph`, even if I instantiate them with an object of my subclass. Is there a better way to filter my graphs than writing a custom `GraphView` subclass for it? Cheers, Patrick