 combine schemas not working in 'paths'

combining schemas in path is not working
e.g. 
```
paths:
 /pets:
 patch:
 requestBody:
 content:
 application/json:
 schema:
 oneOf:
 - $ref: '#/components/schemas/Cat'
 - $ref: '#/components/schemas/Dog'
```

but it's working in

```
components:
 schemas:
 ...
```