code: def gradient(self):
          
          self._init_svd()
          C0 = self._C0.gradient()["Lu"].T
          C1 = self._C1.gradient()["Lu"].T
          grad = {"C0.Lu": kron(C0, self._X).T, "C1.Lu": kron(C1, self._I).T}
          return grad
docs: Gradient of K.
  
          Returns
          -------
          C0 : ndarray
              Derivative of C₀ over its parameters.
          C1 : ndarray
              Derivative of C₁ over its parameters.