@Override
	public CodeBlockReferenceIterator getSources(CodeBlock block, TaskMonitor monitor) throws CancelledException {

        if (!(block.getModel() instanceof OverlapCodeSubModel)) {
			throw new IllegalArgumentException();
		}

        return new SubroutineSourceReferenceIterator(block, monitor);
    }
@see ghidra.program.model.block.CodeBlockModel#getSources(ghidra.program.model.block.CodeBlock, ghidra.util.task.TaskMonitor)
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/block/OverlapCodeSubModel.java