@ ProgramNode (location: (1,0)-(1,13))
├── flags: ∅
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(1,13))
    ├── flags: ∅
    └── body: (length: 1)
        └── @ ArrayNode (location: (1,0)-(1,13))
            ├── flags: newline
            ├── elements: (length: 2)
            │   ├── @ InterpolatedSymbolNode (location: (1,3)-(1,7))
            │   │   ├── flags: ∅
            │   │   ├── opening_loc: ∅
            │   │   ├── parts: (length: 1)
            │   │   │   └── @ EmbeddedStatementsNode (location: (1,3)-(1,7))
            │   │   │       ├── flags: ∅
            │   │   │       ├── opening_loc: (1,3)-(1,5) = "\#{"
            │   │   │       ├── statements:
            │   │   │       │   @ StatementsNode (location: (1,5)-(1,6))
            │   │   │       │   ├── flags: ∅
            │   │   │       │   └── body: (length: 1)
            │   │   │       │       └── @ CallNode (location: (1,5)-(1,6))
            │   │   │       │           ├── flags: variable_call, ignore_visibility
            │   │   │       │           ├── receiver: ∅
            │   │   │       │           ├── call_operator_loc: ∅
            │   │   │       │           ├── name: :a
            │   │   │       │           ├── message_loc: (1,5)-(1,6) = "a"
            │   │   │       │           ├── opening_loc: ∅
            │   │   │       │           ├── arguments: ∅
            │   │   │       │           ├── closing_loc: ∅
            │   │   │       │           └── block: ∅
            │   │   │       └── closing_loc: (1,6)-(1,7) = "}"
            │   │   └── closing_loc: ∅
            │   └── @ InterpolatedSymbolNode (location: (1,8)-(1,12))
            │       ├── flags: ∅
            │       ├── opening_loc: ∅
            │       ├── parts: (length: 1)
            │       │   └── @ EmbeddedStatementsNode (location: (1,8)-(1,12))
            │       │       ├── flags: ∅
            │       │       ├── opening_loc: (1,8)-(1,10) = "\#{"
            │       │       ├── statements:
            │       │       │   @ StatementsNode (location: (1,10)-(1,11))
            │       │       │   ├── flags: ∅
            │       │       │   └── body: (length: 1)
            │       │       │       └── @ CallNode (location: (1,10)-(1,11))
            │       │       │           ├── flags: variable_call, ignore_visibility
            │       │       │           ├── receiver: ∅
            │       │       │           ├── call_operator_loc: ∅
            │       │       │           ├── name: :b
            │       │       │           ├── message_loc: (1,10)-(1,11) = "b"
            │       │       │           ├── opening_loc: ∅
            │       │       │           ├── arguments: ∅
            │       │       │           ├── closing_loc: ∅
            │       │       │           └── block: ∅
            │       │       └── closing_loc: (1,11)-(1,12) = "}"
            │       └── closing_loc: ∅
            ├── opening_loc: (1,0)-(1,3) = "%I["
            └── closing_loc: (1,12)-(1,13) = "]"
