@ ProgramNode (location: (1,0)-(1,23))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(1,23))
    └── body: (length: 1)
        └── @ WhileNode (location: (1,0)-(1,23))
            ├── flags: ∅
            ├── keyword_loc: (1,0)-(1,5) = "while"
            ├── closing_loc: (1,20)-(1,23) = "end"
            ├── predicate:
            │   @ CallNode (location: (1,6)-(1,16))
            │   ├── flags: ∅
            │   ├── receiver:
            │   │   @ ParenthesesNode (location: (1,10)-(1,16))
            │   │   ├── body:
            │   │   │   @ StatementsNode (location: (1,11)-(1,15))
            │   │   │   └── body: (length: 1)
            │   │   │       └── @ TrueNode (location: (1,11)-(1,15))
            │   │   ├── opening_loc: (1,10)-(1,11) = "("
            │   │   └── closing_loc: (1,15)-(1,16) = ")"
            │   ├── call_operator_loc: ∅
            │   ├── name: :!
            │   ├── message_loc: (1,6)-(1,9) = "not"
            │   ├── opening_loc: ∅
            │   ├── arguments: ∅
            │   ├── closing_loc: ∅
            │   └── block: ∅
            └── statements: ∅