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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 _increment(self, n=1):
 """Move forward n tokens in the stream."""

        if self._cur_position >= self.num_tokens-1:
            self._cur_positon = self.num_tokens - 1
            self._finished = True
        else:
            self._cur_position += n