How to use the xiblint.xibutils.get_view_user_defined_attr function in xiblint

def check(self, context):  # type: (XibContext) -> None
        for button in context.tree.findall(".//button"):
            state_normal = button.find("./state[@key='normal']")
            if (
                    state_normal is None or
                    'title' in state_normal.attrib or
                    view_is_accessibility_element(button) is False or
                    view_accessibility_label(button) or
                    get_view_user_defined_attr(button, 'accessibilityFormat')
            ):
                continue

            if 'image' in state_normal.attrib:
                context.error(
                    button,
                    "Button with image '{}' and no title; "
                    "should either have an accessibility label or 'Accessibility Enabled' unchecked",
                    state_normal.attrib['image'])

            if 'backgroundImage' in state_normal.attrib:
                context.error(
                    button,
                    "Button with background image '{}' and no title "
                    "should either have an accessibility label or 'Accessibility Enabled' unchecked",
                    state_normal.attrib['backgroundImage'])

def check(self, context):  # type: (XibContext) -> None
        for image_view in context.tree.findall(".//imageView"):
            if (
                    view_is_accessibility_element(image_view) is True and
                    not view_accessibility_label(image_view) and
                    not get_view_user_defined_attr(image_view, 'accessibilityFormat')
            ):
                context.error(image_view, "Image is accessible but has no accessibility label")

def check_view(context, view):
    accessibility_source_destination_ids = [
        outlet_connection.get('destination') for outlet_connection
        in view.findall("./connections/outletCollection[@property='accessibilitySources']")
    ]

    accessibility_sources = [
        context.tree.find(".//*[@id='{}']".format(destination_id))
        for destination_id in accessibility_source_destination_ids
    ]
    accessibility_sources_count = len(accessibility_sources)

    #
    # Ensure accessibilityFormat iff accessibilitySources
    #
    accessibility_format = get_view_user_defined_attr(view, 'accessibilityFormat')
    if accessibility_format is None and accessibility_sources_count != 0:
        context.error(view, "View has {} accessibility source(s) but accessibilityFormat is unset.",
                      accessibility_sources_count)
        return

    used_identifiers = set(get_accessibility_identifiers(accessibility_format))
    if used_identifiers:
        check_new_format(context, view, accessibility_format, accessibility_sources, used_identifiers)
    else:
        check_old_format(context, view, accessibility_format, accessibility_sources)

def check(self, context):  # type: (XibContext) -> None
        for element in context.tree.findall(".//textField") + context.tree.findall(".//textView"):
            placeholder = (element.get('placeholder') if element.tag == 'textField'
                           else get_view_user_defined_attr(element, 'placeholder'))
            if (
                    placeholder is not None and
                    element.find('./accessibility[@label]') is None and
                    view_is_accessibility_element(element) is not False
            ):
                context.error(
                    element,
                    "{} with placeholder text '{}' but no accessibility label",
                    element.tag, element.get('placeholder'))