@ ProgramNode (location: (1,0)-(6,3))
├── flags: ∅
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(6,3))
    ├── flags: ∅
    └── body: (length: 2)
        ├── @ DefNode (location: (1,0)-(3,3))
        │   ├── flags: newline
        │   ├── name: :f
        │   ├── name_loc: (1,4)-(1,5) = "f"
        │   ├── receiver: ∅
        │   ├── parameters: ∅
        │   ├── body: ∅
        │   ├── locals: []
        │   ├── def_keyword_loc: (1,0)-(1,3) = "def"
        │   ├── operator_loc: ∅
        │   ├── lparen_loc: ∅
        │   ├── rparen_loc: ∅
        │   ├── equal_loc: ∅
        │   └── end_keyword_loc: (3,0)-(3,3) = "end"
        └── @ DefNode (location: (5,0)-(6,3))
            ├── flags: newline
            ├── name: :f
            ├── name_loc: (5,4)-(5,5) = "f"
            ├── receiver: ∅
            ├── parameters: ∅
            ├── body: ∅
            ├── locals: []
            ├── def_keyword_loc: (5,0)-(5,3) = "def"
            ├── operator_loc: ∅
            ├── lparen_loc: ∅
            ├── rparen_loc: ∅
            ├── equal_loc: ∅
            └── end_keyword_loc: (6,0)-(6,3) = "end"
