YAML

!_Schema
types: !_Map_Type
  !_Identifier _Opt: !_TypeDual
    allAlternates:
      - !_ObjectFor(_DualAlternate)
        object: _Opt
        typeParam: T
      - !_ObjectFor(_DualAlternate)
        dual: Null
        object: _Opt
    alternates:
      - !_DualAlternate
        typeParam: T
      - !_DualAlternate
        dual: Null
    name: _Opt
    typeKind: !_TypeKind Dual
    typeParams:
      - !_Named
        name: T

Types

_Dual _Opt

_{Type parameters:} $T

Alternates	Object
	_Opt
	_Opt