@Override
	public boolean exists(String filename, TaskMonitor monitor) {
		File f = new File(rootDir, filename);
		return f.isFile();
	}
Non-task monitor variant of {@link #isValid(TaskMonitor)}.

@return boolean true if this is a valid symbol store
Ghidra/Features/PDB/src/main/java/pdb/symbolserver/LocalSymbolStore.java