@ ProgramNode (location: (1,0)-(3,20))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(3,20))
    └── body: (length: 2)
        ├── @ UnlessNode (location: (1,0)-(1,24))
        │   ├── keyword_loc: (1,0)-(1,6) = "unless"
        │   ├── predicate:
        │   │   @ CallNode (location: (1,7)-(1,10))
        │   │   ├── flags: variable_call
        │   │   ├── receiver: ∅
        │   │   ├── call_operator_loc: ∅
        │   │   ├── name: :foo
        │   │   ├── message_loc: (1,7)-(1,10) = "foo"
        │   │   ├── opening_loc: ∅
        │   │   ├── arguments: ∅
        │   │   ├── closing_loc: ∅
        │   │   └── block: ∅
        │   ├── then_keyword_loc: (1,11)-(1,15) = "then"
        │   ├── statements:
        │   │   @ StatementsNode (location: (1,16)-(1,19))
        │   │   └── body: (length: 1)
        │   │       └── @ CallNode (location: (1,16)-(1,19))
        │   │           ├── flags: variable_call
        │   │           ├── receiver: ∅
        │   │           ├── call_operator_loc: ∅
        │   │           ├── name: :bar
        │   │           ├── message_loc: (1,16)-(1,19) = "bar"
        │   │           ├── opening_loc: ∅
        │   │           ├── arguments: ∅
        │   │           ├── closing_loc: ∅
        │   │           └── block: ∅
        │   ├── consequent: ∅
        │   └── end_keyword_loc: (1,21)-(1,24) = "end"
        └── @ UnlessNode (location: (3,0)-(3,20))
            ├── keyword_loc: (3,0)-(3,6) = "unless"
            ├── predicate:
            │   @ CallNode (location: (3,7)-(3,10))
            │   ├── flags: variable_call
            │   ├── receiver: ∅
            │   ├── call_operator_loc: ∅
            │   ├── name: :foo
            │   ├── message_loc: (3,7)-(3,10) = "foo"
            │   ├── opening_loc: ∅
            │   ├── arguments: ∅
            │   ├── closing_loc: ∅
            │   └── block: ∅
            ├── then_keyword_loc: ∅
            ├── statements:
            │   @ StatementsNode (location: (3,12)-(3,15))
            │   └── body: (length: 1)
            │       └── @ CallNode (location: (3,12)-(3,15))
            │           ├── flags: variable_call
            │           ├── receiver: ∅
            │           ├── call_operator_loc: ∅
            │           ├── name: :bar
            │           ├── message_loc: (3,12)-(3,15) = "bar"
            │           ├── opening_loc: ∅
            │           ├── arguments: ∅
            │           ├── closing_loc: ∅
            │           └── block: ∅
            ├── consequent: ∅
            └── end_keyword_loc: (3,17)-(3,20) = "end"
