@ ProgramNode (location: (0...17))
├── locals: []
└── statements:
    @ StatementsNode (location: (0...17))
    └── body: (length: 1)
        └── @ DefNode (location: (0...17))
            ├── name: :"!@"
            ├── name_loc: (4...6) = "!@"
            ├── receiver: ∅
            ├── parameters: ∅
            ├── body:
            │   @ StatementsNode (location: (8...12))
            │   └── body: (length: 1)
            │       └── @ TrueNode (location: (8...12))
            ├── locals: []
            ├── def_keyword_loc: (0...3) = "def"
            ├── operator_loc: ∅
            ├── lparen_loc: ∅
            ├── rparen_loc: ∅
            ├── equal_loc: ∅
            └── end_keyword_loc: (14...17) = "end"
