@ ProgramNode (location: (1,0)-(1,9))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(1,9))
    └── body: (length: 1)
        └── @ CallNode (location: (1,0)-(1,9))
            ├── flags: ignore_visibility
            ├── receiver: ∅
            ├── call_operator_loc: ∅
            ├── name: :fun
            ├── message_loc: (1,0)-(1,3) = "fun"
            ├── opening_loc: ∅
            ├── arguments:
            │   @ ArgumentsNode (location: (1,4)-(1,6))
            │   ├── flags: ∅
            │   └── arguments: (length: 1)
            │       └── @ ParenthesesNode (location: (1,4)-(1,6))
            │           ├── body: ∅
            │           ├── opening_loc: (1,4)-(1,5) = "("
            │           └── closing_loc: (1,5)-(1,6) = ")"
            ├── closing_loc: ∅
            └── block:
                @ BlockNode (location: (1,7)-(1,9))
                ├── locals: []
                ├── parameters: ∅
                ├── body: ∅
                ├── opening_loc: (1,7)-(1,8) = "{"
                └── closing_loc: (1,8)-(1,9) = "}"