Package Not Found in Netbeans

Hello to everyone ,
I want to write a plugin and follow the lesson on this link.(https://developer.atlassian.com/bitbucket/server/docs/latest/tutorials-and-examples/controlling-when-pull-requests-can-be-merged.html) But I have a problem. I can not add the RepositoryMergeCheck interface on this link to the project.
Import com.atlassian.bitbucket.hook.repository.RepositoryMergeCheck not found.
How can I solve this problem?