code: def commit(self, sha):
          
          url = self._build_url('commits', sha, base_url=self._api)
          json = self._json(self._get(url), 200)
          return RepoCommit(json, self) if json else None
docs: Get a single (repo) commit. See :func:`git_commit` for the Git Data
          Commit.
  
          :param str sha: (required), sha of the commit
          :returns: :class:`RepoCommit <github3.repos.commit.RepoCommit>` if
              successful, otherwise None