def __call__(self, environ, start_response):
        old_method = None
        if self.use_method_override:
            req = None

            # In some odd cases, there's no query string
            try:
                qs = environ['QUERY_STRING']
            except KeyError:
                qs = ''
            if '_method' in qs:
                req = Request(environ)
                req.errors = 'ignore'
                if '_method' in req.GET:
                    old_method = environ['REQUEST_METHOD']
                    environ['REQUEST_METHOD'] = req.GET['_method'].upper()
                    if self.log_debug:
                        log.debug("_method found in QUERY_STRING, altering "
                                  "request method to %s",
                                  environ['REQUEST_METHOD'])
            elif environ['REQUEST_METHOD'] == 'POST' and is_form_post(environ):
                if req is None:
                    req = Request(environ)
                    req.errors = 'ignore'
                if '_method' in req.POST:
                    old_method = environ['REQUEST_METHOD']
                    environ['REQUEST_METHOD'] = req.POST['_method'].upper()
                    if self.log_debug:
                        log.debug("_method found in POST data, altering "
                                  "request method to %s",
                                  environ['REQUEST_METHOD'])

        # Run the actual route matching
        # -- Assignment of environ to config triggers route matching
        if self.singleton:
            config = request_config()
            config.mapper = self.mapper
            config.environ = environ
            match = config.mapper_dict
            route = config.route
        else:
            results = self.mapper.routematch(environ=environ)
            if results:
                match, route = results[0], results[1]
            else:
                match = route = None

        if old_method:
            environ['REQUEST_METHOD'] = old_method

        if not match:
            match = {}
            if self.log_debug:
                urlinfo = "%s %s" % (environ['REQUEST_METHOD'],
                                     environ['PATH_INFO'])
                log.debug("No route matched for %s", urlinfo)
        elif self.log_debug:
            urlinfo = "%s %s" % (environ['REQUEST_METHOD'],
                                 environ['PATH_INFO'])
            log.debug("Matched %s", urlinfo)
            log.debug("Route path: '%s', defaults: %s", route.routepath,
                      route.defaults)
            log.debug("Match dict: %s", match)

        url = URLGenerator(self.mapper, environ)
        environ['wsgiorg.routing_args'] = ((url), match)
        environ['routes.route'] = route
        environ['routes.url'] = url

        if route and route.redirect:
            route_name = '_redirect_%s' % id(route)
            location = url(route_name, **match)
            log.debug("Using redirect route, redirect to '%s' with status"
                      "code: %s", location, route.redirect_status)
            start_response(route.redirect_status,
                           [('Content-Type', 'text/plain; charset=utf8'),
                            ('Location', location)])
            return []

        # If the route included a path_info attribute and it should be used to
        # alter the environ, we'll pull it out
        if self.path_info and 'path_info' in match:
            oldpath = environ['PATH_INFO']
            newpath = match.get('path_info') or ''
            environ['PATH_INFO'] = newpath
            if not environ['PATH_INFO'].startswith('/'):
                environ['PATH_INFO'] = '/' + environ['PATH_INFO']
            environ['SCRIPT_NAME'] += re.sub(
                r'^(.*?)/' + re.escape(newpath) + '$', r'\1', oldpath)

        response = self.app(environ, start_response)

        # Wrapped in try as in rare cases the attribute will be gone already
        try:
            del self.mapper.environ
        except AttributeError:
            pass
        return response
Like :func:`dumps` but writes into a file object.
dataset/ETHPy150Open bbangert/routes/routes/middleware.py/RoutesMiddleware.__call__--crossover with--dataset/ETHPy150Open pallets/flask/flask/json.py/dump