Invalid leaf directive! `since`

Represents a simple 1 input per 1 output recipe, which is the most common usage of custom categories.

Due to its pure simplicity, no configuration is available for this recipe.

It might be required for you to import the package if you encounter any issues (like casting an Array), so better be safe than sorry and add the import at the very top of the file.

ZenScript
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import mods.jei.category.SimpleInputOutput;

SimpleInputOutput extends SimpleJeiCategory. That means all methods available in SimpleJeiCategory are also available in SimpleInputOutput