def render(self, request, context, template_name, expires=None):
        """
        Given a request, a context dictionary and a template name, this renders
        the template with the given context according to the capabilities and
        requested format of the client. An optional final argument is that of
        a timedelta object, which sets additional caching headers for the
        content.
        """
        context.pop('exposes_user_data', None)

        if 'format' in request.REQUEST:
            formats = request.REQUEST['format'].split(',')
            renderers, seen_formats = [], set()
            for format in formats:
                if format in self.FORMATS and format not in seen_formats:
                    renderers.append(self.FORMATS[format])
        elif request.META.get('HTTP_ACCEPT'):
            accepts = self.parse_accept_header(request.META['HTTP_ACCEPT'])
            renderers = MediaType.resolve(accepts, self.FORMATS_BY_MIMETYPE)
        else:
            renderers = [self.FORMATS['html']]

        # Stop external sites from grabbing JSON representations of pages
        # which contain sensitive user information.
        try:
            offsite_referrer = 'HTTP_REFERER' in request.META and \
                request.META['HTTP_REFERER'].split('/')[2] != \
                                                request.META.get('HTTP_HOST')
        except __HOLE__:
            # Malformed referrers (i.e., those not containing a full URL) throw
            # this
            offsite_referrer = True

        for renderer in renderers:
            if renderer.format != 'html' and context.get('exposes_user_data') \
              and offsite_referrer:
                continue
            try:
                response = renderer(request, context, template_name)
            except NotImplementedError:
                continue
            else:
                if expires is not None and not settings.DEBUG and \
                  not getattr(settings, 'NO_CACHE', False):
                    response['Expires'] = formatdate(
                        mktime((datetime.now() + expires).timetuple()))
                    
                    # if expires is negative, then consider this to be no-cache
                    if expires < timedelta(seconds=0):
                        response['Cache-Control'] = 'no-cache'
                    else:
                        response['Cache-Control'] = 'max-age=%d' % \
                                (expires.seconds + expires.days * 24 * 3600)
                    
                return response
        else:
            if 'format' not in request.REQUEST:
                tried_mimetypes = list(itertools.chain(*[r.mimetypes
                                                         for r in renderers]))
                response = HttpResponse(
                  _("Your Accept header didn't contain any supported media ranges.") + \
                  "\n\n" + _("Supported ranges are:") + \
                  "\n\n * %s\n" % '\n * '.join(
                      sorted('%s (%s)' % (f[0].value, f[1].format) for f in
                      self.FORMATS_BY_MIMETYPE if not f[0] in tried_mimetypes)),
                mimetype="text/plain")
            else:
                response = HttpResponse(
                  _("Unable to render this document in this format.") + "\n\n" +
                  _("Supported formats are") + ":\n\n * %s\n" \
                                % '\n * '.join(self.FORMATS.keys()),
                  mimetype="text/plain")
            response.status_code = 406 # Not Acceptable
            return response
dataset/ETHPy150Open mollyproject/mollyproject/molly/utils/views.py/BaseView.render