function isDropAllowed(itemType) {
        if (listSettings.disabled) return false;
        if (!listSettings.externalSources && !dndState.isDragging) return false;
        if (!listSettings.allowedTypes || itemType === null) return true;
        return itemType && listSettings.allowedTypes.indexOf(itemType) != -1;
      }
Checks various conditions that must be fulfilled for a drop to be allowed, including the
dnd-allowed-types attribute. If the item Type is unknown (null), the drop will be allowed.