@Override
		public int getCheckoutVersion(long checkoutId) throws IOException {
			synchronized (fileSystem) {
				ItemCheckoutStatus coStatus = checkoutMgr.getCheckout(checkoutId);
				return coStatus != null ? coStatus.getCheckoutVersion() : -1;
			}
		}
<code>LocalVersionedDbListener</code> provides a listener 
which maintains checkout and history data in response to 
VersionedDatabase callbacks.
Ghidra/Framework/FileSystem/src/main/java/ghidra/framework/store/local/LocalDatabaseItem.java