@ ProgramNode (location: (0...8))
├── locals: []
└── statements:
    @ StatementsNode (location: (0...8))
    └── body: (length: 1)
        └── @ StringNode (location: (0...8))
            ├── opening_loc: (0...8) = "<<~'FOO'"
            ├── content_loc: (9...22) = "  baz\\\n  qux\n"
            ├── closing_loc: (22...26) = "FOO\n"
            └── unescaped: "baz\\\nqux\n"
