def digraph_connected_components(graph: nx.DiGraph, subgraph=None) -> List[List]:
"""
the networkx module does not support deriving connected
components from digraphs (only simple graphs)
this function assumes that connection != reachable
this means there is no difference between connected components
in a simple graph and a digraph
Args:
graph: the input graph to gather components from
Returns:
returns a list of compnents which are lists of node names
"""
if subgraph is None:
subgraph = set(graph.get_nodes())
g = nx.Graph()
for src, tgt in graph.edges():
if src in subgraph and tgt in subgraph:
g.add_edge(src, tgt)
for node in subgraph:
if graph.has_node(node):
g.add_node(node)
return nx.connected_components(g)
