def make_conditional(self, request_or_environ):
        environ = _get_environ(request_or_environ)
        if environ['REQUEST_METHOD'] in ('GET', 'HEAD'):
            # if the date is not in the headers, add it now.  We however
            # will not override an already existing header.  Unfortunately
            # this header will be overriden by many WSGI servers including
            # wsgiref.
            if 'date' not in self.headers:
                self.headers['Date'] = http_date()
            if 'content-length' not in self.headers:
                length = self.calculate_content_length()
                if length is not None:
                    self.headers['Content-Length'] = length
            if not is_resource_modified(environ, self.headers.get('etag'), None,
                                        self.headers.get('last-modified')):
                self.status_code = 304
        return self
Return number of occurrences of value.
dataset/ETHPy150Open Eforcers/gae-flask-todo/lib/werkzeug/wrappers.py/ETagResponseMixin.make_conditional--crossover with--dataset/ETHPy150Open iamteem/redisco/redisco/containers.py/List.count