@ ProgramNode (location: (1,0)-(3,3))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(3,3))
    └── body: (length: 1)
        └── @ CallNode (location: (1,0)-(3,3))
            ├── flags: ∅
            ├── receiver: ∅
            ├── call_operator_loc: ∅
            ├── name: :private
            ├── message_loc: (1,0)-(1,7) = "private"
            ├── opening_loc: ∅
            ├── arguments:
            │   @ ArgumentsNode (location: (1,8)-(3,3))
            │   ├── flags: ∅
            │   └── arguments: (length: 1)
            │       └── @ DefNode (location: (1,8)-(3,3))
            │           ├── name: :f
            │           ├── name_loc: (1,12)-(1,13) = "f"
            │           ├── receiver: ∅
            │           ├── parameters: ∅
            │           ├── body:
            │           │   @ StatementsNode (location: (2,0)-(2,10))
            │           │   └── body: (length: 1)
            │           │       └── @ CallNode (location: (2,0)-(2,10))
            │           │           ├── flags: ∅
            │           │           ├── receiver:
            │           │           │   @ CallNode (location: (2,0)-(2,1))
            │           │           │   ├── flags: variable_call
            │           │           │   ├── receiver: ∅
            │           │           │   ├── call_operator_loc: ∅
            │           │           │   ├── name: :a
            │           │           │   ├── message_loc: (2,0)-(2,1) = "a"
            │           │           │   ├── opening_loc: ∅
            │           │           │   ├── arguments: ∅
            │           │           │   ├── closing_loc: ∅
            │           │           │   └── block: ∅
            │           │           ├── call_operator_loc: (2,1)-(2,2) = "."
            │           │           ├── name: :b
            │           │           ├── message_loc: (2,2)-(2,3) = "b"
            │           │           ├── opening_loc: ∅
            │           │           ├── arguments: ∅
            │           │           ├── closing_loc: ∅
            │           │           └── block:
            │           │               @ BlockNode (location: (2,4)-(2,10))
            │           │               ├── locals: []
            │           │               ├── locals_body_index: 0
            │           │               ├── parameters: ∅
            │           │               ├── body: ∅
            │           │               ├── opening_loc: (2,4)-(2,6) = "do"
            │           │               └── closing_loc: (2,7)-(2,10) = "end"
            │           ├── locals: []
            │           ├── locals_body_index: 0
            │           ├── def_keyword_loc: (1,8)-(1,11) = "def"
            │           ├── operator_loc: ∅
            │           ├── lparen_loc: ∅
            │           ├── rparen_loc: ∅
            │           ├── equal_loc: ∅
            │           └── end_keyword_loc: (3,0)-(3,3) = "end"
            ├── closing_loc: ∅
            └── block: ∅
