public String index() {
		String key = key();
		return key == null ? null : parseIndex(key);
	}
Get the final index of this path

@return the final index
@throws IllegalArgumentException if the final key is not an index, i.e., in brackets
Ghidra/Debug/Framework-TraceModeling/src/main/java/ghidra/trace/model/target/path/KeyPath.java