code: def solve(self, A, F, N, b):
          
          if self.sparselib == 'umfpack':
              umfpack.solve(A, N, b)
  
          elif self.sparselib == 'klu':
              klu.solve(A, F, N, b)
docs: Solve linear system ``Ax = b`` using numeric factorization ``N`` and symbolic factorization ``F``.
          Store the solution in ``b``.
  
          Parameters
          ----------
          A
              Sparse matrix
          F
              Symbolic factorization
          N
              Numeric factorization
          b
              RHS of the equation
  
          Returns
          -------
          None