@property
def is_admissible_slow(self):
    'Checks if there is a path of length 3 with an inner edge from the root to the opposite outer vertex.'
    start_node = self.half_edge
    assert (start_node.color is 'black')
    end_node = self.half_edge.opposite.next.opposite.next.opposite
    assert (end_node.color is 'white')
    start_node = start_node.node_nr
    end_node = end_node.node_nr
    g = self.to_networkx_graph()
    paths = nx.shortest_simple_paths(g, start_node, end_node)
    path_1 = next(paths)
    assert (len(path_1) == 4)
    path_2 = next(paths)
    assert (len(path_2) == 4)
    path_3 = next(paths)
    return (len(path_3) > 4)
Checks if there is a path of length 3 with an inner edge from the root to the opposite outer vertex.
@property
def is_admissible_slow(self):
    
    start_node = self.half_edge
    assert (start_node.color is 'black')
    end_node = self.half_edge.opposite.next.opposite.next.opposite
    assert (end_node.color is 'white')
    start_node = start_node.node_nr
    end_node = end_node.node_nr
    g = self.to_networkx_graph()
    paths = nx.shortest_simple_paths(g, start_node, end_node)
    path_1 = next(paths)
    assert (len(path_1) == 4)
    path_2 = next(paths)
    assert (len(path_2) == 4)
    path_3 = next(paths)
    return (len(path_3) > 4)