Add a new Substitution to this Personalization.

        :type substitution: Substitution

def add_substitution(self, substitution):
        """Add a new Substitution to this Personalization.

        :type substitution: Substitution
        """
        if isinstance(substitution, dict):
            self._substitutions.append(substitution)
        else:
            self._substitutions.append(substitution.get())