def clear(self):
     """Remove all nodes, edges, and attributes from the graph."""
     self.edge_attr.clear()
     self.node_attr.clear()
     self.graph_attr.clear()
     # now "close" existing graph and create a new graph
     name=gv.agnameof(self.handle)
     strict=self.strict
     directed=self.directed
     gv.agclose(self.handle) 
     self.handle=gv.agraphnew(name,strict,directed) 
 def close(self):
     # may be useful to clean up graphviz data
     # this should completely remove all of the existing graphviz data
     gv.agclose(self.handle)