@ ProgramNode (location: (1,0)-(1,16))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(1,16))
    └── body: (length: 1)
        └── @ IfNode (location: (1,0)-(1,16))
            ├── if_keyword_loc: (1,0)-(1,2) = "if"
            ├── predicate:
            │   @ FlipFlopNode (location: (1,3)-(1,7))
            │   ├── left:
            │   │   @ CallNode (location: (1,3)-(1,4))
            │   │   ├── receiver: ∅
            │   │   ├── call_operator_loc: ∅
            │   │   ├── message_loc: (1,3)-(1,4) = "a"
            │   │   ├── opening_loc: ∅
            │   │   ├── arguments: ∅
            │   │   ├── closing_loc: ∅
            │   │   ├── block: ∅
            │   │   ├── flags: variable_call
            │   │   └── name: "a"
            │   ├── right:
            │   │   @ CallNode (location: (1,6)-(1,7))
            │   │   ├── receiver: ∅
            │   │   ├── call_operator_loc: ∅
            │   │   ├── message_loc: (1,6)-(1,7) = "b"
            │   │   ├── opening_loc: ∅
            │   │   ├── arguments: ∅
            │   │   ├── closing_loc: ∅
            │   │   ├── block: ∅
            │   │   ├── flags: variable_call
            │   │   └── name: "b"
            │   ├── operator_loc: (1,4)-(1,6) = ".."
            │   └── flags: ∅
            ├── statements: ∅
            ├── consequent: ∅
            └── end_keyword_loc: (1,13)-(1,16) = "end"