Adds a graph to the quad-graph structure.
Adds a graph to the quad-graph structure. If the index is None, it changes the default graph
Adds a triple to a quad-graph If the index is None it adds the triple to the default graph
Adds a triple to a quad-graph If the index is None it adds the triple to the default graph
Returns the default graph
Returns the default graph
Empty quad-graph
Empty quad-graph
Remove the graph indexed by index
Remove the graph indexed by index