@Override
	public int getNumSources(CodeBlock block, TaskMonitor monitor) throws CancelledException {
    	
    	if (!(block.getModel() instanceof OverlapCodeSubModel)) {
			throw new IllegalArgumentException();
		}
            
    	return SubroutineSourceReferenceIterator.getNumSources(block, monitor);
    }
@see ghidra.program.model.block.CodeBlockModel#getNumSources(ghidra.program.model.block.CodeBlock, ghidra.util.task.TaskMonitor)
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/block/OverlapCodeSubModel.java