This is likely two different tasks. Implement Policies and Implement bin/remove. What is your specific use case here, closing a question should provide most of what you need.

Slowvote already supports policies. Use Edit > Visible To to restrict who can see a poll.

To proceed:

• Implement PhabricatorDestructibleInterface on SlowvotePoll.
• Invoke destruction with bin/remove destroy V123.
• The method should destroy the poll, the options, and the votes.
• See T5409 for a similar task.