private Collection<? extends FunctionTag> getDeletedTags(Program program, TaskMonitor monitor) {

		// 1. Get all tags in the Original database.
		FunctionManagerDB origFunctionManagerDB =
			(FunctionManagerDB) originalPgm.getFunctionManager();
		Collection<? extends FunctionTag> originalTags =
			origFunctionManagerDB.getFunctionTagManager().getAllFunctionTags();

		// 2. Get all tags in the given program database.
		FunctionManagerDB myFunctionManagerDB = (FunctionManagerDB) program.getFunctionManager();
		Collection<? extends FunctionTag> programTags =
			myFunctionManagerDB.getFunctionTagManager().getAllFunctionTags();

		// 3. Determine which ones are in Original but not in the given program.
		originalTags.removeAll(programTags);

		return originalTags;
	}
Compares the given program against Original to determine if any tags differ 
between the two. Any tags in Original that are NOT in the given program 
indicate deletions.

@param program the program version 
@param monitor
@return database IDs from the FunctionTagAdapter table that were deleted
Ghidra/Features/Base/src/main/java/ghidra/app/merge/listing/FunctionTagListingMerger.java