protected boolean isEntryNode(CodeBlock block) throws CancelledException {
		CodeBlockReferenceIterator iter = block.getSources(taskMonitor);
		boolean isSource = true;
		while (iter.hasNext()) {
			isSource = false;
			if (iter.next().getFlowType().isCall()) {
				return true;
			}
		}
		return isSource;
	}
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