code: def _enumerate_paths(self, prefix_path):
          
          for branch in self.branches:
              path = [prefix_path, branch]
              if branch.child_branchset is not None:
                  for subpath in branch.child_branchset._enumerate_paths(path):
                      yield subpath
              else:
                  yield path
docs: Recursive (private) part of :func:`enumerate_paths`. Returns generator
          of recursive lists of two items, where second item is the branch object
          and first one is itself list of two items.