@ ProgramNode (location: (1,0)-(1,8))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(1,8))
    └── body: (length: 1)
        └── @ CallNode (location: (1,0)-(1,8))
            ├── flags: ∅
            ├── receiver: ∅
            ├── call_operator_loc: ∅
            ├── name: :p
            ├── message_loc: (1,0)-(1,1) = "p"
            ├── opening_loc: ∅
            ├── arguments:
            │   @ ArgumentsNode (location: (1,2)-(1,8))
            │   ├── flags: ∅
            │   └── arguments: (length: 1)
            │       └── @ StringNode (location: (1,2)-(1,8))
            │           ├── flags: ∅
            │           ├── opening_loc: (1,2)-(1,8) = "<<~\"E\""
            │           ├── content_loc: (2,0)-(3,0) = "  x\\n   y\n"
            │           ├── closing_loc: (3,0)-(4,0) = "E\n"
            │           └── unescaped: "x\n   y\n"
            ├── closing_loc: ∅
            └── block: ∅
