code: def stream(self, request, counter=0):
          '''Returns an iterable over strings.
          '''
          if self._children:
              for child in self._children:
                  if isinstance(child, String):
                      yield from child.stream(request, counter+1)
                  else:
                      yield chilf stream(self, request, counter=0):
          '''Returns an iterable over strings.
          '''
          if self._children:
              for child in self._children:
                  if isinstance(child, String):
                      yield from child.stream(request, counter+1)
                  else:
                      yield child
docs: Returns an iterable over strings.