code: def _new_stream(self, idx):
          
          # Get the stream index from the candidate pool
          stream_index = self.stream_idxs_[idx]
  
          # Activate the Streamer, and get the weights
          self.streams_[idx] = self.streamers[stream_index].iterate()
  
          # Reset the sample count to zero
          self.stream_counts_[idx] = 0
docs: Activate a new stream, given the index into the stream pool.
  
          BaseMux's _new_stream simply chooses a new stream and activates it.
          For special behavior (ie Weighted streams), you must override this
          in a child class.
  
          Parameters
          ----------
          idx : int, [0:n_streams - 1]
              The stream index to replace