Fix networkx stub; location of subgraph_view, etc. (#11385)

Author: NeilGirdhar

stubs/networkx/networkx/classes/__init__.pyi

@@ -2,5 +2,6 @@ from . import coreviews as coreviews, filters as filters, graphviews as graphvie
 from .digraph import DiGraph as DiGraph
 from .function import *
 from .graph import Graph as Graph
+from .graphviews import reverse_view as reverse_view, subgraph_view as subgraph_view
 from .multidigraph import MultiDiGraph as MultiDiGraph
 from .multigraph import MultiGraph as MultiGraph