@ ProgramNode (location: (0...16))
├── locals: []
└── statements:
    @ StatementsNode (location: (0...16))
    └── body: (length: 1)
        └── @ CallNode (location: (0...16))
            ├── receiver:
            │   @ CallNode (location: (0...1))
            │   ├── receiver: ∅
            │   ├── call_operator_loc: ∅
            │   ├── message_loc: (0...1) = "a"
            │   ├── opening_loc: ∅
            │   ├── arguments: ∅
            │   ├── closing_loc: ∅
            │   ├── block: ∅
            │   ├── flags: variable_call
            │   └── name: "a"
            ├── call_operator_loc: (1...2) = "."
            ├── message_loc: (2...4) = "!="
            ├── opening_loc: (4...5) = "("
            ├── arguments:
            │   @ ArgumentsNode (location: (5...15))
            │   └── arguments: (length: 2)
            │       ├── @ TrueNode (location: (5...9))
            │       └── @ TrueNode (location: (11...15))
            ├── closing_loc: (15...16) = ")"
            ├── block: ∅
            ├── flags: ∅
            └── name: "!="
