code: def L(self):
          
          m = len(self._tril1[0])
          self._L[self._tril1] = self._Lu.value[:m]
          self._L[self._diag] = exp(self._Lu.value[m:])
          return self._L
docs: Lower-triangular matrix L such that K = LLᵀ + ϵI.
  
          Returns
          -------
          L : (d, d) ndarray
              Lower-triangular matrix.