code: def get_root_graph(self,root):
        
        children = self.get_children(root)
        g = Graph()
        nodes = [root]+children
        for node in nodes: g.add_node(node)
        node_ids = [x.id for x in nodes]
        edges = [x for x in self._edges.values() if x.node1.id in node_ids and x.node2.id in node_ids]
        for e in edges: g.add_edge(e)
        return g
docs: Return back a graph containing just the root and children