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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 dKdiag_dX(self, dL_dKdiag, X, target):
 """Gradient of diagonal of covariance with respect to X."""

        target += 2.*self.mapping.df_dX(dL_dKdiag[:, None], X)*self.mapping.f(X)