@ ProgramNode (location: (0...10))
├── locals: []
└── statements:
    @ StatementsNode (location: (0...10))
    └── body: (length: 1)
        └── @ InterpolatedStringNode (location: (0...10))
            ├── opening_loc: (0...1) = "\""
            ├── parts: (length: 2)
            │   ├── @ StringNode (location: (1...3))
            │   │   ├── opening_loc: ∅
            │   │   ├── content_loc: (1...3) = "a "
            │   │   ├── closing_loc: ∅
            │   │   └── unescaped: "a "
            │   └── @ EmbeddedStatementsNode (location: (3...9))
            │       ├── opening_loc: (3...5) = "\#{"
            │       ├── statements:
            │       │   @ StatementsNode (location: (5...8))
            │       │   └── body: (length: 1)
            │       │       └── @ StringNode (location: (5...8))
            │       │           ├── opening_loc: (5...6) = "'"
            │       │           ├── content_loc: (6...7) = "b"
            │       │           ├── closing_loc: (7...8) = "'"
            │       │           └── unescaped: "b"
            │       └── closing_loc: (8...9) = "}"
            └── closing_loc: (9...10) = "\""
