@ ProgramNode (location: (0...27))
├── locals: []
└── statements:
    @ StatementsNode (location: (0...27))
    └── body: (length: 2)
        ├── @ UndefNode (location: (0...10))
        │   ├── names: (length: 1)
        │   │   └── @ SymbolNode (location: (6...10))
        │   │       ├── opening_loc: (6...7) = ":"
        │   │       ├── value_loc: (7...10) = "foo"
        │   │       ├── closing_loc: ∅
        │   │       └── unescaped: "foo"
        │   └── keyword_loc: (0...5) = "undef"
        └── @ UndefNode (location: (11...27))
            ├── names: (length: 2)
            │   ├── @ SymbolNode (location: (17...21))
            │   │   ├── opening_loc: (17...18) = ":"
            │   │   ├── value_loc: (18...21) = "foo"
            │   │   ├── closing_loc: ∅
            │   │   └── unescaped: "foo"
            │   └── @ SymbolNode (location: (23...27))
            │       ├── opening_loc: (23...24) = ":"
            │       ├── value_loc: (24...27) = "bar"
            │       ├── closing_loc: ∅
            │       └── unescaped: "bar"
            └── keyword_loc: (11...16) = "undef"
