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