@ ProgramNode (location: (0...10))
├── locals: []
└── statements:
    @ StatementsNode (location: (0...10))
    └── body: (length: 1)
        └── @ InterpolatedStringNode (location: (0...10))
            ├── opening_loc: (0...1) = "\""
            ├── parts: (length: 2)
            │   ├── @ EmbeddedStatementsNode (location: (1...5))
            │   │   ├── opening_loc: (1...3) = "\#{"
            │   │   ├── statements:
            │   │   │   @ StatementsNode (location: (3...4))
            │   │   │   └── body: (length: 1)
            │   │   │       └── @ CallNode (location: (3...4))
            │   │   │           ├── receiver: ∅
            │   │   │           ├── call_operator_loc: ∅
            │   │   │           ├── message_loc: (3...4) = "a"
            │   │   │           ├── opening_loc: ∅
            │   │   │           ├── arguments: ∅
            │   │   │           ├── closing_loc: ∅
            │   │   │           ├── block: ∅
            │   │   │           ├── flags: variable_call
            │   │   │           └── name: "a"
            │   │   └── closing_loc: (4...5) = "}"
            │   └── @ EmbeddedStatementsNode (location: (5...9))
            │       ├── opening_loc: (5...7) = "\#{"
            │       ├── statements:
            │       │   @ StatementsNode (location: (7...8))
            │       │   └── body: (length: 1)
            │       │       └── @ CallNode (location: (7...8))
            │       │           ├── receiver: ∅
            │       │           ├── call_operator_loc: ∅
            │       │           ├── message_loc: (7...8) = "b"
            │       │           ├── opening_loc: ∅
            │       │           ├── arguments: ∅
            │       │           ├── closing_loc: ∅
            │       │           ├── block: ∅
            │       │           ├── flags: variable_call
            │       │           └── name: "b"
            │       └── closing_loc: (8...9) = "}"
            └── closing_loc: (9...10) = "\""