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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 add_reaction(self, reaction_id):
 """Add reaction to model"""


        if reaction_id in self._reaction_set:
            return

        reaction = self._database.get_reaction(reaction_id)
        self._reaction_set.add(reaction_id)
        for compound, _ in reaction.compounds:
            self._compound_set.add(compound)