The example under the 'Model Composition' section is 'Inheritance and Polymorphism' has the wrong indentation on this page:
https://swagger.io/docs/specification/data-models/inheritance-and-polymorphism/
This can be confusing since there is no verbal explanation at what level 'allOf' should be included.
This is what we see:

This is what it should look like:

Hope this is of help!