wip: mirror_crud_to_nxcg

[aMahanna]

Introduces a new parameter (mirror_crud_to_nxcg) to the nxadb.Graph constructor.

If set to True, any CRUD operations performed on the ArangoDB Graph will be reflected on the cached cuGraph Graph, if it exists.

# Assumption: NVIDIA GPU available, and `nx-cugraph` installed

import os
import networkx as nx
import nx_arangodb as nxadb

os.environ["..."] = ...

G = nxadb.Graph(name="MyGraph", mirror_crud_to_nxcg=True)

res = nx.pagerank(G) # Pulls the data as an NetworkX-cuGraph object, and caches it to G.nxcg_Graph

If mirror_crud_to_nxcg is False

G.add_node(999, foo="bar") # does not update the `G.nxcg_graph` object

assert G.number_of_nodes() == G.nxcg_graph.number_of_nodes() + 1

print(G.nxcg_graph.nodes[999]) # KeyError

If mirror_crud_to_nxcg is True

G.add_node(999, foo="bar") # updates the `G.nxcg_graph` object

assert G.number_of_nodes() == G.nxcg_graph.number_of_nodes()

print(G.nxcg_graph.nodes[999]) # Works