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