private static Schema createRegisterSchema() {
		Schema schema = new Schema(1, "Keys", new Field[] { StringField.INSTANCE },
			new String[] { "Register Context" });
		return schema;
	}
Class maintain a list of prototypes and corresponding IDs.
NOTE: The prototype ID will be negative if the prototype is in a
delay slot.
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/database/code/PrototypeManager.java