MaybeBool
        
        Description:
        public enum MaybeBool
        
        
          A 'boolean' type that has a distinct 'unset' state.
          Since:
          0.3.1
         
        
        
        Content:
        Enum values:
        
          - FALSE - False (this value was set from its 
              default of UNSET).
- TRUE - True (this value was set from its 
              default of UNSET).
- UNSET - This value is explicitly unset.