@ 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...7))
            │   │   ├── opening_loc: (1...3) = "\#{"
            │   │   ├── statements:
            │   │   │   @ StatementsNode (location: (3...6))
            │   │   │   └── body: (length: 1)
            │   │   │       └── @ StringNode (location: (3...6))
            │   │   │           ├── opening_loc: (3...4) = "'"
            │   │   │           ├── content_loc: (4...5) = "a"
            │   │   │           ├── closing_loc: (5...6) = "'"
            │   │   │           └── unescaped: "a"
            │   │   └── closing_loc: (6...7) = "}"
            │   └── @ StringNode (location: (7...9))
            │       ├── opening_loc: ∅
            │       ├── content_loc: (7...9) = " b"
            │       ├── closing_loc: ∅
            │       └── unescaped: " b"
            └── closing_loc: (9...10) = "\""
