<!--
  Note: if the issue is about documentation or the website, please file it at:
  https://github.com/reactjs/reactjs.org/issues/new
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**Do you want to request a *feature* or report a *bug*?**

bug.

**What is the current behavior?**

```js
  renderer.create(
    <Fragment>
      <Fragment>foo</Fragment>
    </Fragment>
  )
  .toTree()
```

> Invariant Violation: toTree() does not yet know how to handle nodes with tag=10

https://codesandbox.io/s/olky92m01y

**What is the expected behavior?**

returns a tree.

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**

16.2.0

props: {[propName: string]: any},
  children: null | Array<ReactTestRendererNode>,
  $$typeof?: Symbol, 
|};
type ReactTestRendererNode = ReactTestRendererJSON | string;
type Container = {|
  children: Array<Instance | TextInstance>,
  createNodeMock: Function,
  tag: 'CONTAINER',
|};
type Props = Object;
type Instance = {|
  type: string,
  props: Object,
  children: Array<Instance | TextInstance>,
  rootContainerInstance: Container,
  tag: 'INSTANCE',
|};
type TextInstance = {|
  text: string,
  tag: 'TEXT',
|};
type FindOptions = $Shape<{
  
  
  deep: boolean,
}>;
export type Predicate = (node: ReactTestInstance) => ?boolean;
const UPDATE_SIGNAL = {};
function getPublicInstance(inst: Instance | TextInstance): * {