private long getResultIDFromOriginalID(long originalSymbolID) {
		try {
			return originalResolvedSymbols.get(originalSymbolID);
		}
		catch (NoValueException e) {
			if (resultPgm.getSymbolTable().getSymbol(originalSymbolID) != null) {
				return originalSymbolID;
			}
		}
		return -1;
	}
Actually merges (sets or removes) the indicated external program name in
program1 based on the same external program name in program2
@param program1 the program to merge into.
@param program2 the program to get the merge information from.
@param idGroup the symbol ID group for the external program (Library) to merge.
@param monitor task monitor for feedback or canceling the merge.s
Ghidra/Features/Base/src/main/java/ghidra/app/merge/listing/ExternalProgramMerger.java