code: def play_response(self, request):
          
          for index, response in self._responses(request):
              if self.play_counts[index] == 0:
                  self.play_counts[index] += 1
                  return response
          # The cassette doesn't contain the request asked for.
          raise UnhandledHTTPRequestError(
              "The cassette (%r) doesn't contain the request (%r) asked for"
              % (self._path, request)
          )
docs: Get the response corresponding to a request, but only if it
          hasn't been played back before, and mark it as played