@ ProgramNode (location: (1,0)-(8,4))
├── flags: ∅
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(8,4))
    ├── flags: ∅
    └── body: (length: 2)
        ├── @ StringNode (location: (1,0)-(1,4))
        │   ├── flags: newline
        │   ├── opening_loc: (1,0)-(1,4) = "<<-E"
        │   ├── content_loc: (2,0)-(5,0) = "    1 \\\n    2\n    3\n"
        │   ├── closing_loc: (5,0)-(6,0) = "E\n"
        │   └── unescaped: "    1     2\n    3\n"
        └── @ InterpolatedStringNode (location: (8,0)-(8,4))
            ├── flags: newline
            ├── opening_loc: (8,0)-(8,4) = "<<~E"
            ├── parts: (length: 3)
            │   ├── @ StringNode (location: (9,0)-(10,0))
            │   │   ├── flags: static_literal, frozen
            │   │   ├── opening_loc: ∅
            │   │   ├── content_loc: (9,0)-(10,0) = "    1 \\\n"
            │   │   ├── closing_loc: ∅
            │   │   └── unescaped: "1 "
            │   ├── @ StringNode (location: (10,0)-(11,0))
            │   │   ├── flags: static_literal, frozen
            │   │   ├── opening_loc: ∅
            │   │   ├── content_loc: (10,0)-(11,0) = "    2\n"
            │   │   ├── closing_loc: ∅
            │   │   └── unescaped: "2\n"
            │   └── @ StringNode (location: (11,0)-(12,0))
            │       ├── flags: static_literal, frozen
            │       ├── opening_loc: ∅
            │       ├── content_loc: (11,0)-(12,0) = "    3\n"
            │       ├── closing_loc: ∅
            │       └── unescaped: "3\n"
            └── closing_loc: (12,0)-(13,0) = "E\n"
