code: def construct_result_generator_middleware(result_generators):
      
      def result_generator_middleware(make_request, web3):
          def middleware(method, params):
              if method in result_generators:
                  result = result_generators[method](method, params)
                  return {'result': result}
              else:
                  return make_request(method, params)
          return middleware
      return result_generator_middleware
docs: Constructs a middleware which intercepts requests for any method found in
      the provided mapping of endpoints to generator functions, returning
      whatever response the generator function returns.  Callbacks must be
      functions with the signature `fn(method, params)`.