itly
call the `iron-form`'s `submit` method.

  Example:

    <paper-button raised onclick="submitForm()">Submit</paper-button>

    function submitForm() {
      document.getElementById('iron-form').submit();
    }

If you are not using the `allow-redirect` mode, then you also have the option of
customizing the request sent to the server. To do so, you can listen to the `iron-form-presubmit`
event, and modify the form's [`iron-ajax`](https://elements.polymer-project.org/elements/iron-ajax)
object. However,