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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 smoothing(self, vs=None):
 r"""Return the smoothing of a function over a sequence of N variables. The *vs* argument is a sequence of :math:`N` Boolean variables. The *smoothing* of :math:`f(x_1, x_2, \dots, x_i, \dots, x_n)` with respect to variable :math:`x_i` is: :math:`S_{x_i}(f) = f_{x_i} + f_{x_i'}` This is the same as the existential quantification operator: :math:`\exists \{x_1, x_2, \dots\} \: f` """

        return functools.reduce(operator.or_, self.iter_cofactors(vs))