public void setSource(FcgVertex source) {
		if (this.source != null) {
			throw new IllegalStateException("Cannot change graph source once it has been created");
		}

		this.source = source;
		addVertex(source);
	}
Sets the source vertex from which the graph is created
@param source the source vertex from which the graph is created
Ghidra/Features/GraphFunctionCalls/src/main/java/functioncalls/graph/FunctionCallGraph.java