code: def merge(self, commit_message=github.GithubObject.NotSet, commit_title=github.GithubObject.NotSet, merge_method=github.GithubObject.NotSet, sha=github.GithubObject.NotSet):
          
          assert commit_message is github.GithubObject.NotSet or isinstance(commit_message, (str, unicode)), commit_message
          assert commit_title is github.GithubObject.NotSet or isinstance(commit_title, (str, unicode)), commit_title
          assert merge_method is github.GithubObject.NotSet or isinstance(merge_method, (str, unicode)), merge_method
          assert sha is github.GithubObject.NotSet or isinstance(sha, (str, unicode)), sha
          post_parameters = dict()
          if commit_message is not github.GithubObject.NotSet:
              post_parameters["commit_message"] = commit_message
          if commit_title is not github.GithubObject.NotSet:
              post_parameters["commit_title"] = commit_title
          if merge_method is not github.GithubObject.NotSet:
              post_parameters["merge_method"] = merge_method
          if sha is not github.GithubObject.NotSet:
              post_parameters["sha"] = sha
          headers, data = self._requester.requestJsonAndCheck(
              "PUT",
              self.url + "/merge",
              input=post_parameters
          )
          return github.PullRequestMergeStatus.PullRequestMergeStatus(self._requester, headers, data, completed=True)
docs: :calls: `PUT /repos/:owner/:repo/pulls/:number/merge <http://developer.github.com/v3/pulls>`_
          :param commit_message: string
          :rtype: :class:`github.PullRequestMergeStatus.PullRequestMergeStatus`