Denotes a special builder that is used for building special block types. Used in BlockBuilder#withType
This class was added by a mod with mod-id
contenttweaker. So you need to have this mod installed if you want to use this feature.
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.
BlockTypeBuilder implements the following interfaces. That means all methods defined in these interfaces are also available in BlockTypeBuilder