@ ProgramNode (location: (1,0)-(1,10))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(1,10))
    └── body: (length: 1)
        └── @ ClassVariableWriteNode (location: (1,0)-(1,10))
            ├── name: :@@var
            ├── name_loc: (1,0)-(1,5) = "@@var"
            ├── value:
            │   @ IntegerNode (location: (1,8)-(1,10))
            │   └── flags: decimal
            └── operator_loc: (1,6)-(1,7) = "="
