# File lib/mechanize/form.rb, line 257
  def add_button_to_query(button)
    unless button.node.document == @form_node.document then
      message =
        "#{button.inspect} does not belong to the same page as " \
        "the form #{@name.inspect} in #{@page.uri}"

      raise ArgumentError, message
    end

    @clicked_buttons << button
  end