class_docstr: An AST (a tree) for a simple arithmetic expression.
code: def _arg_string(self, pos):
      arg = self.args[pos]
      return (
          f"{arg._to_string(pos, self.prio, self.assoc)}"
          if isinstance(arg, Expression)
          else str(arg)
      )
  
imports: import random
label_desc: Use image node_id 9 for calling the Expression obj's underlying member method code with example usage: obj._arg_string(pos) and returns: unknown