/guava/guava/src/com/google/common/graph/StandardNetwork.java
N referenceNode = edgeToReferenceNode.get ( edge ) ;
checkNotNull(node); throw new IllegalArgumentException(String.format(NODE_NOT_IN_GRAPH, node)); } return connections; } final N checkedReferenceNode(E edge) { <extra_id_0> if (referenceNode == null) { checkNotNull(edge); throw new IllegalArgumentException(String.format(EDGE_NOT_IN_GRAPH, edge)); } return referenceNode; }