@ ProgramNode (location: (0...18))
├── locals: []
└── statements:
    @ StatementsNode (location: (0...18))
    └── body: (length: 1)
        └── @ IfNode (location: (0...18))
            ├── if_keyword_loc: (0...2) = "if"
            ├── predicate:
            │   @ IntegerNode (location: (3...4))
            │   └── flags: decimal
            ├── statements: ∅
            ├── consequent:
            │   @ IfNode (location: (6...18))
            │   ├── if_keyword_loc: (6...11) = "elsif"
            │   ├── predicate:
            │   │   @ IntegerNode (location: (12...13))
            │   │   └── flags: decimal
            │   ├── statements: ∅
            │   ├── consequent: ∅
            │   └── end_keyword_loc: (15...18) = "end"
            └── end_keyword_loc: (15...18) = "end"
