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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 K(self, X, X2=None):
 """ Kernel function applied on inputs X and X2. In the stationary case there is an inner function depending on the distances from X to X2, called r. K(X, X2) = K_of_r((X-X2)**2) """

        r = self._scaled_dist(X, X2)
        return self.K_of_r(r)