code: def tree(self, sha):
          
          json = None
          if sha:
              url = self._build_url('git', 'trees', sha, base_url=self._api)
              json = self._json(self._get(url), 200)
          return Tree(json, self) if json else None
docs: Get a tree.
  
          :param str sha: (required), sha of the object for this tree
          :returns: :class:`Tree <github3.git.Tree>`