public Slot getSlot(int slot) {
        if (slot < 0 || slot >= this.inventory.getSize()) {
            throw new IllegalArgumentException("Invalid slot id: " + slot);
        }

        if (invalidated) {
            return new DummySlot(this, slot);
        }

        return this.slots.computeIfAbsent(slot, i -> new SimpleSlot(this, i));
    }
Gets the initial title which was set when this GUI was made

@return the initial title used when this GUI was made
helper/src/main/java/me/lucko/helper/menu/Gui.java