@ ProgramNode (location: (0...22))
├── locals: []
└── statements:
    @ StatementsNode (location: (0...22))
    └── body: (length: 2)
        ├── @ LambdaNode (location: (0...11))
        │   ├── locals: [:a]
        │   ├── operator_loc: (0...2) = "->"
        │   ├── opening_loc: (8...9) = "{"
        │   ├── closing_loc: (10...11) = "}"
        │   ├── parameters:
        │   │   @ BlockParametersNode (location: (3...7))
        │   │   ├── parameters:
        │   │   │   @ ParametersNode (location: (3...7))
        │   │   │   ├── requireds: (length: 0)
        │   │   │   ├── optionals: (length: 0)
        │   │   │   ├── rest: ∅
        │   │   │   ├── posts: (length: 0)
        │   │   │   ├── keywords: (length: 1)
        │   │   │   │   └── @ KeywordParameterNode (location: (3...7))
        │   │   │   │       ├── name: :a
        │   │   │   │       ├── name_loc: (3...5) = "a:"
        │   │   │   │       └── value:
        │   │   │   │           @ IntegerNode (location: (6...7))
        │   │   │   │           └── flags: decimal
        │   │   │   ├── keyword_rest: ∅
        │   │   │   └── block: ∅
        │   │   ├── locals: (length: 0)
        │   │   ├── opening_loc: ∅
        │   │   └── closing_loc: ∅
        │   └── body: ∅
        └── @ LambdaNode (location: (13...22))
            ├── locals: [:a]
            ├── operator_loc: (13...15) = "->"
            ├── opening_loc: (19...20) = "{"
            ├── closing_loc: (21...22) = "}"
            ├── parameters:
            │   @ BlockParametersNode (location: (16...18))
            │   ├── parameters:
            │   │   @ ParametersNode (location: (16...18))
            │   │   ├── requireds: (length: 0)
            │   │   ├── optionals: (length: 0)
            │   │   ├── rest: ∅
            │   │   ├── posts: (length: 0)
            │   │   ├── keywords: (length: 1)
            │   │   │   └── @ KeywordParameterNode (location: (16...18))
            │   │   │       ├── name: :a
            │   │   │       ├── name_loc: (16...18) = "a:"
            │   │   │       └── value: ∅
            │   │   ├── keyword_rest: ∅
            │   │   └── block: ∅
            │   ├── locals: (length: 0)
            │   ├── opening_loc: ∅
            │   └── closing_loc: ∅
            └── body: ∅
