code: def get_stream_if_exists(self, stream_id):
          
          stream = self.get_stream(stream_id)
          try:
              stream.get_data_type(use_cached=True)
          except NoSuchStreamException:
              return None
          else:
              return stream
docs: Return a reference to a stream with the given ``stream_id`` if it exists
  
          This works similar to :py:meth:`get_stream` but will return None if the
          stream is not already created.
  
          :param stream_id: The path of the stream on Device Cloud
          :raises TypeError: if the stream_id provided is the wrong type
          :raises ValueError: if the stream_id is not properly formed
          :return: :class:`.DataStream` instance with the provided stream_id
          :rtype: :class:`~DataStream`