Null graph:
( )
( )
Several isolated vertices:
( )
( )
Isolated vertices with self-loops:
( 1 )
( 0 )
Small directed graph:
OUT
( 1 2 0 )
( 0 1 4 )
IN
( 2 1 0 )
( 4 1 0 )
ALL
( 2 1 0 )
( 4 1 0 )
Small undirected multigraph:
( 4 3 )
( 1 2 )
Directed acyclic graph:
OUT
( )
( )
IN
( )
( )
