docs: def classify_pr_synced_state(pr: PullRequestDetails) -> Optional[bool]:
      """
      References:
          https://developer.github.com/v3/pulls/#get-a-single-pull-request
          https://developer.github.com/v4/enum/mergestatestatus/
      """
      state = pr.payload['mergeable_state'].lower()
      classification = {
          'behind': False,
          'clean': True,
      }
      return classification.get(state, None)