@ ProgramNode (location: (1,0)-(1,14))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(1,14))
    └── body: (length: 1)
        └── @ UnlessNode (location: (1,0)-(1,14))
            ├── keyword_loc: (1,4)-(1,10) = "unless"
            ├── predicate:
            │   @ CallNode (location: (1,11)-(1,14))
            │   ├── flags: variable_call, ignore_visibility
            │   ├── receiver: ∅
            │   ├── call_operator_loc: ∅
            │   ├── name: :foo
            │   ├── message_loc: (1,11)-(1,14) = "foo"
            │   ├── opening_loc: ∅
            │   ├── arguments: ∅
            │   ├── closing_loc: ∅
            │   └── block: ∅
            ├── then_keyword_loc: ∅
            ├── statements:
            │   @ StatementsNode (location: (1,0)-(1,3))
            │   └── body: (length: 1)
            │       └── @ CallNode (location: (1,0)-(1,3))
            │           ├── flags: variable_call, ignore_visibility
            │           ├── receiver: ∅
            │           ├── call_operator_loc: ∅
            │           ├── name: :bar
            │           ├── message_loc: (1,0)-(1,3) = "bar"
            │           ├── opening_loc: ∅
            │           ├── arguments: ∅
            │           ├── closing_loc: ∅
            │           └── block: ∅
            ├── consequent: ∅
            └── end_keyword_loc: ∅