docs: def checkout(self, revision_id):
          """
          :param revision_id: :class:`revision.data.Revision` ID.
          :type revision_id: str
          """
          index = 0
          found = False
          for revision in self.revisions:
              if revision.revision_id == revision_id:
                  self.current_index = index
                  found = True
  
              index += 1
  
          if not found:
              raise RuntimeError("")