One vertex: ( ) Vertex with multiple edges, IGRAPH_IN, IGRAPH_MULTIPLE: ( 2 2 ) Vertex with multiple edges, IGRAPH_OUT, IGRAPH_MULTIPLE: ( 1 2 ) Vertex with multiple edges, IGRAPH_ALL, IGRAPH_MULTIPLE: ( 1 2 2 2 ) Vertex with multiple edges, undirected, IGRAPH_MULTIPLE: ( 1 2 2 2 ) Vertex with multiple edges, IGRAPH_IN, IGRAPH_NO_MULTIPLE: ( 2 ) Vertex with multiple edges, IGRAPH_OUT, IGRAPH_NO_MULTIPLE: ( 1 2 ) Vertex with multiple edges, IGRAPH_ALL, IGRAPH_NO_MULTIPLE: ( 1 2 ) Vertex with multiple edges, undirected, IGRAPH_NO_MULTIPLE: ( 1 2 ) Vertex 1 with loop, IGRAPH_OUT, IGRAPH_NO_LOOPS: ( 3 ) Vertex 1 with loop, IGRAPH_ALL, IGRAPH_NO_LOOPS: ( 0 3 ) Vertex 1 with loop, undirected, IGRAPH_NO_LOOPS: ( 0 3 ) Vertex 1 with loop, IGRAPH_OUT, IGRAPH_LOOPS_ONCE: ( 1 3 ) Vertex 1 with loop, IGRAPH_ALL, IGRAPH_LOOPS_ONCE: ( 0 1 3 ) Vertex 1 with loop, undirected, IGRAPH_LOOPS_ONCE: ( 0 1 3 ) Vertex 1 with loop, IGRAPH_ALL, IGRAPH_LOOPS_TWICE: ( 0 1 1 3 ) Vertex 1 with loop, undirected, IGRAPH_LOOPS_TWICE: ( 0 1 1 3 ) Graph with 2 edges from 0 to 1, and 2 from 1 to 0, IGRAPH_ALL, IGRAPH_MULTIPLE: ( 1 1 1 1 ) Graph with 1 edge from 0 to 1, and 2 from 1 to 0, IGRAPH_ALL, IGRAPH_MULTIPLE: ( 1 1 1 ) Trying IGRAPH_LOOPS_TWICE with IGRAPH_OUT: Trying invalid vertex ID: Trying invalid mode: