private AttributedVertex getEntryNexusVertex(AttributedGraph graph) {
		AttributedVertex vertex = graph.getVertex(ENTRY_NEXUS_NAME);
		if (vertex == null) {
			vertex = graph.addVertex(ENTRY_NEXUS_NAME, ENTRY_NEXUS_NAME);
			vertex.setAttribute("VertexType", ENTRY_NEXUS);
		}
		return vertex;
	}
Determine if the specified block is an entry node.
@param block the basic block to test
@return true  if the specified block is an entry node.
@throws CancelledException if the operation is cancelled
Ghidra/Features/ProgramGraph/src/main/java/ghidra/graph/program/BlockGraphTask.java