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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _new_stream(self, idx):
 """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 """

        # 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