private String getVertexId(CodeBlock bb) {
		// vertex has attributes of Name       = Label
		//                          Address    = address of blocks start
		//                          VertexType = flow type of vertex
		Address addr = bb.getFirstStartAddress();
		if (addr.isExternalAddress()) {
			Symbol s = bb.getModel().getProgram().getSymbolTable().getPrimarySymbol(addr);
			return s.getName(true);
		}
		return addr.toString();
	}
Set the maximum number of code lines which will be used per block when
showCode is enabled.
@param maxLines maximum number of code lines
Ghidra/Features/ProgramGraph/src/main/java/ghidra/graph/program/BlockGraphTask.java