@ ProgramNode (location: (1,0)-(8,1))
├── flags: ∅
├── locals: [:o]
└── statements:
    @ StatementsNode (location: (1,0)-(8,1))
    ├── flags: ∅
    └── body: (length: 2)
        ├── @ DefNode (location: (1,0)-(3,3))
        │   ├── flags: newline
        │   ├── name: :a
        │   ├── name_loc: (1,4)-(1,5) = "a"
        │   ├── receiver: ∅
        │   ├── parameters:
        │   │   @ ParametersNode (location: (1,6)-(1,8))
        │   │   ├── flags: ∅
        │   │   ├── requireds: (length: 0)
        │   │   ├── optionals: (length: 0)
        │   │   ├── rest: ∅
        │   │   ├── posts: (length: 0)
        │   │   ├── keywords: (length: 1)
        │   │   │   └── @ RequiredKeywordParameterNode (location: (1,6)-(1,8))
        │   │   │       ├── flags: ∅
        │   │   │       ├── name: :b
        │   │   │       └── name_loc: (1,6)-(1,8) = "b:"
        │   │   ├── keyword_rest: ∅
        │   │   └── block: ∅
        │   ├── body:
        │   │   @ StatementsNode (location: (2,0)-(2,6))
        │   │   ├── flags: ∅
        │   │   └── body: (length: 1)
        │   │       └── @ ReturnNode (location: (2,0)-(2,6))
        │   │           ├── flags: newline
        │   │           ├── keyword_loc: (2,0)-(2,6) = "return"
        │   │           └── arguments: ∅
        │   ├── locals: [:b]
        │   ├── def_keyword_loc: (1,0)-(1,3) = "def"
        │   ├── operator_loc: ∅
        │   ├── lparen_loc: ∅
        │   ├── rparen_loc: ∅
        │   ├── equal_loc: ∅
        │   └── end_keyword_loc: (3,0)-(3,3) = "end"
        └── @ LocalVariableWriteNode (location: (5,0)-(8,1))
            ├── flags: newline
            ├── name: :o
            ├── depth: 0
            ├── name_loc: (5,0)-(5,1) = "o"
            ├── value:
            │   @ HashNode (location: (5,4)-(8,1))
            │   ├── flags: static_literal
            │   ├── opening_loc: (5,4)-(5,5) = "{"
            │   ├── elements: (length: 1)
            │   │   └── @ AssocNode (location: (6,0)-(7,1))
            │   │       ├── flags: static_literal
            │   │       ├── key:
            │   │       │   @ SymbolNode (location: (6,0)-(6,2))
            │   │       │   ├── flags: static_literal, forced_us_ascii_encoding
            │   │       │   ├── opening_loc: ∅
            │   │       │   ├── value_loc: (6,0)-(6,1) = "a"
            │   │       │   ├── closing_loc: (6,1)-(6,2) = ":"
            │   │       │   └── unescaped: "a"
            │   │       ├── value:
            │   │       │   @ IntegerNode (location: (7,0)-(7,1))
            │   │       │   ├── flags: static_literal, decimal
            │   │       │   └── value: 1
            │   │       └── operator_loc: ∅
            │   └── closing_loc: (8,0)-(8,1) = "}"
            └── operator_loc: (5,2)-(5,3) = "="
