@ ProgramNode (location: (1,0)-(1,9))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(1,9))
    └── body: (length: 1)
        └── @ CallNode (location: (1,0)-(1,9))
            ├── flags: ∅
            ├── receiver: ∅
            ├── call_operator_loc: ∅
            ├── name: :a
            ├── message_loc: (1,0)-(1,1) = "a"
            ├── opening_loc: (1,1)-(1,2) = "("
            ├── arguments:
            │   @ ArgumentsNode (location: (1,2)-(1,8))
            │   ├── flags: contains_keyword_splat
            │   └── arguments: (length: 2)
            │       ├── @ CallNode (location: (1,2)-(1,3))
            │       │   ├── flags: variable_call
            │       │   ├── receiver: ∅
            │       │   ├── call_operator_loc: ∅
            │       │   ├── name: :b
            │       │   ├── message_loc: (1,2)-(1,3) = "b"
            │       │   ├── opening_loc: ∅
            │       │   ├── arguments: ∅
            │       │   ├── closing_loc: ∅
            │       │   └── block: ∅
            │       └── @ KeywordHashNode (location: (1,5)-(1,8))
            │           ├── flags: ∅
            │           └── elements: (length: 1)
            │               └── @ AssocSplatNode (location: (1,5)-(1,8))
            │                   ├── value:
            │                   │   @ IntegerNode (location: (1,7)-(1,8))
            │                   │   └── flags: decimal
            │                   └── operator_loc: (1,5)-(1,7) = "**"
            ├── closing_loc: (1,8)-(1,9) = ")"
            └── block: ∅
