allof.yaml

components:
  schemas:
    Pet:
      type: object
      required:
        - pet_type
      properties:
        pet_type:
          type: string
    Dog:
      allOf: 
        - $ref: '#/components/schemas/Pet'
        - type: object
          properties:
            bark:
              type: boolean
            breed:
              type: string
              enum: [Dingo, Husky, Retriever, Shepherd]
    Cat:
      allOf: 
        - $ref: '#/components/schemas/Pet'
        - type: object
          properties:
            hunts:
              type: boolean
            age:
              type: integer