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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 substitution(self, substitution):
 """Add substitutions to the email :param value: Add substitutions to the email :type value: Substitution, list(Substitution) """

        if isinstance(substitution, list):
            for s in substitution:
                self.add_substitution(s)
        else:
            self.add_substitution(substitution)