class SyntaxTree::ArgParen

def format(q)
  unless arguments
    q.text("()")
    return
  end
  q.text("(")
  q.group do
    q.indent do
      q.breakable_empty
      q.format(arguments)
      q.if_break { q.text(",") } if q.trailing_comma? && trailing_comma?
    end
    q.breakable_empty
  end
  q.text(")")
end