code: def _check_convergence(self, F):
          
          normF = linalg.norm(F, Inf)
  
          if normF < self.tolerance:
              converged = True
          else:
              converged = False
              if self.verbose:
                  logger.info("Difference: %.3f" % (normF - self.tolerance))
  
          return converged
docs: Checks if the solution has converged to within the specified
              tolerance.