How to use the wagtailmedia.permissions.permission_policy function in wagtailmedia

def edit(request, media_id):
    Media = get_media_model()
    MediaForm = get_media_form(Media)

    media = get_object_or_404(Media, id=media_id)

    if not permission_policy.user_has_permission_for_instance(request.user, 'change', media):
        return permission_denied(request)

    if request.POST:
        original_file = media.file
        form = MediaForm(request.POST, request.FILES, instance=media, user=request.user)
        if form.is_valid():
            if 'file' in form.changed_data:
                # if providing a new media file, delete the old one.
                # NB Doing this via original_file.delete() clears the file field,
                # which definitely isn't what we want...
                original_file.storage.delete(original_file.name)
            media = form.save()

            # Reindex the media entry to make sure all tags are indexed
            for backend in get_search_backends():
                backend.add(media)

def is_editable_by_user(self, user):
        from wagtailmedia.permissions import permission_policy
        return permission_policy.user_has_permission_for_instance(user, 'change', self)

from wagtail.admin.utils import PermissionPolicyChecker, permission_denied, popular_tags_for_model
from wagtail.core.models import Collection
from wagtail.search.backends import get_search_backends

from wagtailmedia.forms import get_media_form
from wagtailmedia.models import get_media_model
from wagtailmedia.permissions import permission_policy
from wagtailmedia.utils import paginate

if WAGTAIL_VERSION < (2, 5):
    from wagtail.admin.forms import SearchForm
else:
    from wagtail.admin.forms.search import SearchForm


permission_checker = PermissionPolicyChecker(permission_policy)


@permission_checker.require_any('add', 'change', 'delete')
@vary_on_headers('X-Requested-With')
def index(request):
    Media = get_media_model()

    # Get media files (filtered by user permission)
    media = permission_policy.instances_user_has_any_permission_for(
        request.user, ['change', 'delete']
    )

    # Ordering
    if 'ordering' in request.GET and request.GET['ordering'] in ['title', '-created_at']:
        ordering = request.GET['ordering']
    else:

from wagtail.admin.modal_workflow import render_modal_workflow
from wagtail.admin.utils import PermissionPolicyChecker
from wagtail.core.models import Collection

from wagtailmedia.models import get_media_model
from wagtailmedia.permissions import permission_policy
from wagtailmedia.utils import paginate

if WAGTAIL_VERSION < (2, 5):
    from wagtail.admin.forms import SearchForm
    pagination_template = "wagtailadmin/shared/pagination_nav.html"
else:
    from wagtail.admin.forms.search import SearchForm
    pagination_template = "wagtailadmin/shared/ajax_pagination_nav.html"

permission_checker = PermissionPolicyChecker(permission_policy)


def get_media_json(media):
    """
    helper function: given a media, return the json to pass back to the
    chooser panel
    """

    return {
        'id': media.id,
        'title': media.title,
        'edit_link': reverse('wagtailmedia:edit', args=(media.id,))
    }


def chooser(request):