React-transition-group: findDOMNode is depreciated. Use a ref instead.

[bluefire2121]

What is the current behavior?
When using React.StrictMode, a warning appears that indicates findDOMNode is depreciated.

What is the expected behavior?
The expected behavior is the error/warning doesn't exists. Facebook recommends adding a ref directly to the element you want to reference. Learn more about using refs safely here: https://fb.me/react-strict-mode-find-node

Could you provide a CodeSandbox demo reproducing the bug?
With Material-UI, place inside and include a component or any component that utilizes a transition (since Material-UI transitions are based on react-transition-group).

[bluefire2121]

Added screenshot of error

[jquense]

please search before opening new issues, thanks!

[bluefire2121]

Please link to the duplicate prior to closing issue