Represents a value that can assume three values, instead of a simple boolean that can only assume two values.

Importing the class

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.

import crafttweaker.api.predicate.TriState;

Extending Enum<TriState>

TriState extends Enum<TriState>. That means all methods available in Enum<TriState> are also available in TriState