subelement?

subelement.yml

---
proviver_subnet_map:                                                               
  - name: aws                                                                      
    region_azs:                                                                    
      - us-east-1:                                                                 
        - a                                                                        
        - c                                                                        
      - us-east-2:                                                                 
        - a                                                                        
        - d                                                                        
      - us-west-2:                                                                 
        - a