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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_nmr_prize_pool(self, round_num=0, tournament=1):
 """Get NMR prize pool for the given round and tournament. Args: round_num (int, optional):
 The round you are interested in, defaults to current round. tournament (int, optional):
 ID of the tournament, defaults to 1 Returns: decimal.Decimal: prize pool in NMR Raises: Value Error: in case of invalid round number """

        tournaments = self.get_competitions(tournament)
        tournaments.sort(key=lambda t: t['number'])
        if round_num == 0:
            t = tournaments[-1]
        else:
            tournaments = [t for t in tournaments if t['number'] == round_num]
            if len(tournaments) == 0:
                raise ValueError("invalid round number")
            t = tournaments[0]
        return t['prizePoolNmr']