How to use the webob.exc.HTTPMethodNotAllowed function in WebOb

def default(self, req, image_id, id, body=None):
        """This will cover the missing 'show' and 'create' actions"""
        raise webob.exc.HTTPMethodNotAllowed()

def reject(self, req, allowed_methods, *args, **kwargs):
        LOG.debug("The method %s is not allowed for this resource",
                  req.environ['REQUEST_METHOD'])
        raise webob.exc.HTTPMethodNotAllowed(
            headers=[('Allow', allowed_methods)])

def check_method(remainder, params):
            if request.method != 'POST':
                if self.redir is not None:
                    redirect(self.redir)
                raise exc.HTTPMethodNotAllowed(headers={'Allow': 'POST'})
        before_validate(check_method)(func)

def __call__(self, request):
        """Handles a call to this application.

        Returns 204 if the request is acceptable to the limiter, else a 403
        is returned with a relevant header indicating when the request
        *will* succeed.
        """
        if request.method != "POST":
            raise webob.exc.HTTPMethodNotAllowed()

        try:
            info = dict(jsonutils.loads(request.body))
        except ValueError:
            raise webob.exc.HTTPBadRequest()

        username = request.path_info_pop()
        verb = info.get("verb")
        path = info.get("path")

        delay, error = self._limiter.check_for_delay(verb, path, username)

        if delay:
            headers = {"X-Wait-Seconds": "%.2f" % delay}
            return webob.exc.HTTPForbidden(headers=headers, explanation=error)
        else:

'min_disk': ,
                    'min_ram': ,
                    'store': ,
                    'status': ,
                    'created_at': ,
                    'updated_at': ,
                    'deleted_at': |,
                    'properties': {'distro': 'Ubuntu 10.04 LTS', {...}}
                 }, {...}]
            }

        """
        if req.method == 'HEAD':
            msg = (_("This operation is currently not permitted on "
                     "Glance images details."))
            raise HTTPMethodNotAllowed(explanation=msg,
                                       headers={'Allow': 'GET'},
                                       body_template='${explanation}')
        self._enforce(req, 'get_images')
        params = self._get_query_params(req)
        try:
            images = registry.get_images_detail(req.context, **params)
            # Strip out the Location attribute. Temporary fix for
            # LP Bug #755916. This information is still coming back
            # from the registry, since the API server still needs access
            # to it, however we do not return this potential security
            # information to the API end user...
            for image in images:
                redact_loc(image, copy_dict=False)
                self._enforce_read_protected_props(image, req)
        except exception.Invalid as e:
            raise HTTPBadRequest(explanation=e.msg, request=req)

:raises:
            ``exc.HTTPNotFound`` if no route matched or
            ``exc.HTTPMethodNotAllowed`` if a route matched but the HTTP
            method was not allowed.
        """
        method_not_allowed = False
        for route in self.match_routes:
            try:
                match = route.match(request)
                if match:
                    return match
            except exc.HTTPMethodNotAllowed:
                method_not_allowed = True

        if method_not_allowed:
            raise exc.HTTPMethodNotAllowed()

        raise exc.HTTPNotFound()

:raises:
            ``exc.HTTPNotFound`` if no route matched or
            ``exc.HTTPMethodNotAllowed`` if a route matched but the HTTP
            method was not allowed.
        """
        method_not_allowed = False
        for route in self.match_routes:
            try:
                match = route.match(request)
                if match:
                    return match
            except exc.HTTPMethodNotAllowed:
                method_not_allowed = True

        if method_not_allowed:
            raise exc.HTTPMethodNotAllowed()

        raise exc.HTTPNotFound()

def handle_not_allowed(environ, start_response):
    """Return a 405 response when method is not allowed.

    If _methods are in routing_args, send an allow header listing
    the methods that are possible on the provided URL.
    """
    _methods = util.wsgi_path_item(environ, '_methods')
    headers = {}
    if _methods:
        headers['allow'] = str(_methods)
    raise webob.exc.HTTPMethodNotAllowed(
        ('The method specified is not allowed for this resource.'),
        headers=headers, json_formatter=util.json_error_formatter)

"""Matches this route against the current request.

        :raises:
            ``exc.HTTPMethodNotAllowed`` if the route defines :attr:`methods`
            and the request method isn't allowed.

        .. seealso:: :meth:`BaseRoute.match`.
        """
        match = self.regex.match(urllib.unquote(request.path))
        if not match or self.schemes and request.scheme not in self.schemes:
            return None

        if self.methods and request.method not in self.methods:
            # This will be caught by the router, so routes with different
            # methods can be tried.
            raise exc.HTTPMethodNotAllowed()

        args, kwargs = _get_route_variables(match, self.defaults.copy())
        return self, args, kwargs

def patch(self, allocation_ident, patch):
        """Update an existing allocation.

        :param allocation_ident: UUID or logical name of an allocation.
        :param patch: a json PATCH document to apply to this allocation.
        """
        if not api_utils.allow_allocation_update():
            raise webob_exc.HTTPMethodNotAllowed(_(
                "The API version does not allow updating allocations"))

        context = api.request.context
        rpc_allocation = api_utils.check_allocation_policy_and_retrieve(
            'baremetal:allocation:update', allocation_ident)
        self._validate_patch(patch)
        names = api_utils.get_patch_values(patch, '/name')
        for name in names:
            if name and not api_utils.is_valid_logical_name(name):
                msg = _("Cannot update allocation with invalid name "
                        "'%(name)s'") % {'name': name}
                raise exception.Invalid(msg)
        allocation_dict = rpc_allocation.as_dict()
        allocation = Allocation(**api_utils.apply_jsonpatch(allocation_dict,
                                                            patch))
        # Update only the fields that have changed