def to_ast
      args_ast = args.map { |arg| arg.respond_to?(:to_ast) ? arg.to_ast : arg }
      [name, args_ast]
    end
def to_ast
      args_ast = args.map { |arg| arg.respond_to?(:to_ast) ? arg.to_ast : arg }
      [name, args_ast]
    end
Return a simple AST representation of this function

 @return [Array]

 @api public