code: def get_pull_request_thread(self, repository_id, pull_request_id, thread_id, project=None, iteration=None, base_iteration=None):
          
          route_values = {}
          if project is not None:
              route_values['project'] = self._serialize.url('project', project, 'str')
          if repository_id is not None:
              route_values['repositoryId'] = self._serialize.url('repository_id', repository_id, 'str')
          if pull_request_id is not None:
              route_values['pullRequestId'] = self._serialize.url('pull_request_id', pull_request_id, 'int')
          if thread_id is not None:
              route_values['threadId'] = self._serialize.url('thread_id', thread_id, 'int')
          query_parameters = {}
          if iteration is not None:
              query_parameters['$iteration'] = self._serialize.query('iteration', iteration, 'int')
          if base_iteration is not None:
              query_parameters['$baseIteration'] = self._serialize.query('base_iteration', base_iteration, 'int')
          response = self._send(http_method='GET',
                                location_id='ab6e2e5d-a0b7-4153-b64a-a4efe0d49449',
                                version='5.1-preview.1',
                                route_values=route_values,
                                query_parameters=query_parameters)
          return self._deserialize('GitPullRequestCommentThread', response)
docs: GetPullRequestThread.
          [Preview API] Retrieve a thread in a pull request.
          :param str repository_id: The repository ID of the pull request's target branch.
          :param int pull_request_id: ID of the pull request.
          :param int thread_id: ID of the thread.
          :param str project: Project ID or project name
          :param int iteration: If specified, thread position will be tracked using this iteration as the right side of the diff.
          :param int base_iteration: If specified, thread position will be tracked using this iteration as the left side of the diff.
          :rtype: :class:`<GitPullRequestCommentThread> <azure.devops.v5_1.git.models.GitPullRequestCommentThread>`