private boolean isDummy(V v) {
		return v != null && mutableGraph.isDummy(v);
	}
Returns all nodes that dominate the given vertex.  A node 'a' dominates node 'b' if 
all paths from start to 'b' contain 'a'.  

@param a the vertex
@return the dominating vertices
Ghidra/Framework/Graph/src/main/java/ghidra/graph/algo/ChkDominanceAlgorithm.java