Link to iitemdestroyspeed

The IItemDestroySpeed function can be added to an Item and will determine the item's block breaking speed.

Importing the package

Link to importing-the-package

It might be required for you to import the package if you encounter any issues, so better be safe than sorry and add the import.
import mods.contenttweaker.IItemDestroySpeed;

The IItemDestroySpeed is a function with the following parameters:

The function needs to return a float value.