How to use the klein.Requirer function in klein

from twisted.web.template import tags, slot
from klein import Klein, Plating, Form, Field, Requirer, SessionProcurer
from klein.interfaces import ISession
from klein.storage.memory import MemorySessionStore

app = Klein()

sessions = MemorySessionStore()

requirer = Requirer()

@requirer.prerequisite([ISession])
def procurer(request):
    return SessionProcurer(sessions).procureSession(request)


style = Plating(tags=tags.html(
    tags.head(tags.title("yay")),
    tags.body(tags.div(slot(Plating.CONTENT))))
)

@style.routed(
    requirer.require(
        app.route("/", methods=["POST"]),
        foo=Field.integer(minimum=3, maximum=10), bar=Field.text(),
    ),

from twisted.web.util import Redirect

if TYPE_CHECKING:
    from hyperlink import DecodedURL
    # silence flake8 for type-checking
    (ISessionProcurer, Deferred, IRequest, Dict, Tag, Any, RenderableForm,
     ISessionStore, DecodedURL)

app = Klein()

def bootstrap(x):
    # type: (str) -> str
    return "https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/" + x

requirer = Requirer()

style = Plating(
    tags=tags.html(
        tags.head(
            tags.link(rel="stylesheet",
                      href=bootstrap("css/bootstrap.min.css"),
                      crossorigin="anonymous"),
            # tags.script(
            #     src=bootstrap("js/bootstrap.min.js"),
            #     crossorigin="anonymous"
            # ),
            tags.title("hooray")
        ),
        tags.body(
            tags.nav(Class="navbar navbar-expand-lg navbar-light bg-light")(
                tags.a("Navbar", Class="navbar-brand",