question: public DagIterator ( Graph pattern ) { for ( Edge edge : pattern . getEdges ( ) ) { if ( Edges . isDirectedEdge ( edge ) || Edges . isUndirectedEdge ( edge ) ) { continue ; } throw new IllegalArgumentException ( "The graph may consist only of " + "directed and undirected edges: " + edge ) ; } decoratedGraphs . add ( new DecoratedGraph ( pattern ) ) ; }
target:  The given pattern must be a pattern. If it does not consist entirely of directed and undirected edges and if it is not acyclic, it is rejected.