subscriptions-transport-ws subscriptionClient: Observable<ExecutionResult<ExecutionResultDataDefault>> is not assignable to type SubscriptionForwarder

[DanielLarsenNZ]

I love this library but I am having trouble getting the Subscription client set up. Here is my code (copied from your docs):

import Vue from 'vue'
import App from './App.vue'
import { createClient } from 'vue-gql';
import { SubscriptionClient } from 'subscriptions-transport-ws';

const subscriptionClient = new SubscriptionClient('ws://localhost:4001/graphql', {});

const client = createClient({
  url: 'http://localhost:4000/graphql',
  subscriptionForwarder: op => subscriptionClient.request(op)
});
Vue.config.productionTip = false

new Vue({
  render: h => h(App),
}).$mount('#app')

When I npm run serve this (with vue-cli) I get Typescript error:

10:3 Type '(op: Operation) => Observable<ExecutionResult<ExecutionResultDataDefault>>' is not assignable to type 'SubscriptionForwarder'.
  Type 'Observable<ExecutionResult<ExecutionResultDataDefault>>' is not assignable to type 'ObservableLike<OperationResult>'.
    Types of property 'subscribe' are incompatible.
      Type '(observer: Observer<ExecutionResult<ExecutionResultDataDefault>>) => { unsubscribe: () => void; }' is not assignable to type '(observer: ObserverLike<OperationResult>) => Unsub'.
        Types of parameters 'observer' and 'observer' are incompatible.
          Type 'ObserverLike<OperationResult>' is not assignable to type 'Observer<ExecutionResult<ExecutionResultDataDefault>>'.
            Types of property 'next' are incompatible.
              Type '(value: OperationResult) => void' is not assignable to type '(value: ExecutionResult<ExecutionResultDataDefault>) => void'.
                Types of parameters 'value' and 'value' are incompatible.
                  Type 'ExecutionResult<ExecutionResultDataDefault>' is not assignable to type 'OperationResult'.                           Property 'data' is optional in type 'ExecutionResult<ExecutionResultDataDefault>' but required in type 'OperationResult'.
     8 | const client = createClient({
     9 |   url: 'http://localhost:4000/graphql',
  > 10 |   subscriptionForwarder: op => subscriptionClient.request(op)
       |   ^
    11 | });
    12 | Vue.config.productionTip = false
    13 |
Version: typescript 3.5.3
Time: 4819ms

package.json:

{
  "name": "foobar",
  "version": "0.1.0",
  "private": true,
  "scripts": {
    "serve": "vue-cli-service serve",
    "build": "vue-cli-service build"
  },
  "dependencies": {
    "graphql": "^14.5.8",
    "subscriptions-transport-ws": "^0.9.16",
    "vue": "^2.6.10",
    "vue-gql": "^0.2.3"
  },
  "devDependencies": {
    "@vue/cli-plugin-typescript": "^4.1.0",
    "@vue/cli-service": "^4.1.0",
    "typescript": "~3.5.3",
    "vue-template-compiler": "^2.6.10"
  }
}

What am I doing wrong here? 🤔