Make the graph a complete graph.
        
        @attention: This will modify the current graph.

def complete(self):
        """
        Make the graph a complete graph.
        
        @attention: This will modify the current graph.
        """
        for each in self.nodes():
            for other in self.nodes():
                if (each != other and not self.has_edge((each, other))):
                    self.add_edge((each, other))