@ ProgramNode (location: (0...7))
├── locals: []
└── statements:
    @ StatementsNode (location: (0...7))
    └── body: (length: 1)
        └── @ YieldNode (location: (0...7))
            ├── keyword_loc: (0...5) = "yield"
            ├── lparen_loc: (5...6) = "("
            ├── arguments: ∅
            └── rparen_loc: (6...7) = ")"
