private void initializeEntries() throws InvalidInputException {
		baseTiles = resource.extractTiles(baseType);
		altTiles = resource.extractTiles(altType);
		if (baseTiles.length == 0 || altTiles.length == 0) {
			throw new InvalidInputException(
				"Could not find matching resources for action: join_dual_class");
		}
		tileSize = baseTiles[0].getSize();
		if (tileSize != altTiles[0].getSize()) {
			throw new InvalidInputException(
				"Storage class register sizes do not match for action: join_dual_class");
		}
	}
Find the first ParamEntry matching the baseType, and the first matching altType.
@throws InvalidInputException if the required elements are not available in the resource list
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/lang/protorules/MultiSlotDualAssign.java