private Symbol getLatestSymbol() {
			SymbolTable latestSymbolTable = latestPgm.getSymbolTable();
			return (latestID != -1) ? latestSymbolTable.getSymbol(latestID) : null;
		}
Creates a group of IDs in the four programs for a particular symbol.
@param resultID the symbol's ID in the Result program or -1 if it doesn't exist in Result.
@param originalID the symbol's ID in the Original program or -1 if it doesn't exist in Original.
@param latestID the symbol's ID in the Latest program or -1 if it doesn't exist in Latest.
@param myID the symbol's ID in the My program or -1 if it doesn't exist in My.
Ghidra/Features/Base/src/main/java/ghidra/app/merge/listing/ExternalProgramMerger.java