@ ProgramNode (location: (0...13))
├── locals: []
└── statements:
    @ StatementsNode (location: (0...13))
    └── body: (length: 1)
        └── @ CallNode (location: (0...13))
            ├── receiver: ∅
            ├── call_operator_loc: ∅
            ├── message_loc: (0...1) = "a"
            ├── opening_loc: (1...2) = "("
            ├── arguments:
            │   @ ArgumentsNode (location: (2...12))
            │   └── arguments: (length: 2)
            │       ├── @ StringNode (location: (2...6))
            │       │   ├── opening_loc: (2...3) = "\""
            │       │   ├── content_loc: (3...5) = "\\n"
            │       │   ├── closing_loc: (5...6) = "\""
            │       │   └── unescaped: "\n"
            │       └── @ TrueNode (location: (8...12))
            ├── closing_loc: (12...13) = ")"
            ├── block: ∅
            ├── flags: ∅
            └── name: "a"
