def METHOD_NAME(url_root, username, id_string):
    """Returns Twilio integration documentation."""
    urla = url_root + reverse(
        "sms_submission_api", kwargs={"username": username, "service": "twilio"}
    )
    urlb = url_root + reverse(
        "sms_submission_form_api",
        kwargs={"username": username, "id_string": id_string, "service": "twilio"},
    )
    doc = (
        "<p>"
        + _("%(service)s Instructions:")
        % {"service": '<a href="https://twilio.com">' "Twilio's SMS Request</a>"}
        + "</p><ol><li>"
        + _("Sign in to Twilio.com and go your Application.")
        + "</li><li>"
        + _(
            "Follow instructions to add one of the following URLs, "
            "selecting the HTTP POST method:"
        )
        + '<br /><span class="sms_autodoc_example">%(urla)s'
        + "<br />%(urlb)s</span><br />"
        + "</li></ol><p>"
        + _(
            "That's it. Now Send an SMS Formhub submission to your Twilio"
            " phone number. It will create a submission on Formhub."
        )
        + "</p>"
    ) % {"urla": urla, "urlb": urlb}
    return doc