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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 get_trend(self, item, nb=6):
 """Get the trend regarding to the last nb values. The trend is the diff between the mean of the last nb values and the current one. """

        raw_history = self.get_raw_history(item=item, nb=nb)
        if raw_history is None or len(raw_history) < nb:
            return None
        last_nb = [v[1] for v in raw_history]
        return last_nb[-1] - mean(last_nb[:-1])