@Override
	public AddressSet getAddressSet(AddressSetView sourceAddressSet) {
		if (sourceAddressSet == null) {
			return null;
		}
		if (sourceAddressSet.getNumAddresses() > 1) {
			throw new AddressTranslationException(
				"An external address translator can only handle a single address at a time, if that.");
		}
		AddressSet destinationSet = new AddressSet();
		if (sourceAddressSet.isEmpty()) {
			return destinationSet;
		}
		Address sourceAddress = sourceAddressSet.getMinAddress();
		Address destinationAddress = addressMap.get(sourceAddress);
		if (destinationAddress != null) {
			destinationSet.add(destinationAddress);
		}
		throw new AddressTranslationException(
			"The specified source address set never had an external address pair added to the translator.");
	}
ExternalsAddressTranslator is a translator that can be used for merging external functions and
labels. <br>
Important: Before using this with ProgramMerge you must add all the address pairs that
will translate the external address space address from the source program to the address
in the destination program.
Ghidra/Features/Base/src/main/java/ghidra/app/merge/listing/ExternalsAddressTranslator.java