@ ProgramNode (location: (1,0)-(1,7))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(1,7))
    └── body: (length: 1)
        └── @ CallNode (location: (1,0)-(1,7))
            ├── flags: ignore_visibility
            ├── receiver:
            │   @ SelfNode (location: (1,0)-(1,4))
            ├── call_operator_loc: ∅
            ├── name: :[]
            ├── message_loc: (1,4)-(1,7) = "[1]"
            ├── opening_loc: (1,4)-(1,5) = "["
            ├── arguments:
            │   @ ArgumentsNode (location: (1,5)-(1,6))
            │   ├── flags: ∅
            │   └── arguments: (length: 1)
            │       └── @ IntegerNode (location: (1,5)-(1,6))
            │           ├── flags: decimal
            │           └── value: 1
            ├── closing_loc: (1,6)-(1,7) = "]"
            └── block: ∅