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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 dKd_dVar(self, X, X2=None):
 		""" 		Derivative of Kernel function wrt variance 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. 		dKd_dVar(X, X2) = dKdVar_of_r((X-X2)**2) 		"""

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