Returns the Bull Graph
The Bull Graph has 5 nodes and 5 edges. It is a planar undirected graph in the form of a triangle with two disjoint pendant edges  The name comes from the triangle and pendant edges representing respectively the body and legs of a bull.
- create_usingNetworkX graph constructor, optional (default=nx.Graph)
Graph type to create. If graph instance, then cleared before populated.
- Gnetworkx Graph
A bull graph with 5 nodes