Null graph:
( )

Singleton graph:
( 0 )

Path with isolated vertex:
( 1 0 1 )

Undirected path graph:
( 4 3 2 3 4 )

Directed path graph:
( 4 3 2 1 0 )

Undirected star:
( 1 2 2 2 2 2 2 2 2 2 )

Out-star:
( 1 2 2 2 2 2 2 2 2 2 )

Out-star, IGRAPH_OUT:
( 1 0 0 0 0 0 0 0 0 0 )
