@ ProgramNode (location: (0...12))
├── locals: []
└── statements:
    @ StatementsNode (location: (0...12))
    └── body: (length: 1)
        └── @ CallNode (location: (0...12))
            ├── receiver: ∅
            ├── call_operator_loc: ∅
            ├── message_loc: (0...4) = "puts"
            ├── opening_loc: ∅
            ├── arguments:
            │   @ ArgumentsNode (location: (5...12))
            │   └── arguments: (length: 1)
            │       └── @ KeywordHashNode (location: (5...12))
            │           └── elements: (length: 1)
            │               └── @ AssocNode (location: (5...12))
            │                   ├── key:
            │                   │   @ SymbolNode (location: (5...9))
            │                   │   ├── opening_loc: (5...6) = "'"
            │                   │   ├── value_loc: (6...7) = "a"
            │                   │   ├── closing_loc: (7...9) = "':"
            │                   │   └── unescaped: "a"
            │                   ├── value:
            │                   │   @ HashNode (location: (10...12))
            │                   │   ├── opening_loc: (10...11) = "{"
            │                   │   ├── elements: (length: 0)
            │                   │   └── closing_loc: (11...12) = "}"
            │                   └── operator_loc: ∅
            ├── closing_loc: ∅
            ├── block: ∅
            ├── flags: ∅
            └── name: "puts"
