def set_val(self, key, val, do_callback=True):
        new_pairs = []
        added = False
        self._add_key(key)
        for p in self._pairs:
            if self._ef_key(p[0]) == self._ef_key(key):
                if not added:
                    # only add the first instance
                    new_pairs.append((key, val))
                    added = True
            else:
                new_pairs.append(p)
        if not added:
            new_pairs.append((key, val))
        self._pairs = new_pairs

        if do_callback:
            self._mod_callback()
Test the custom ``django_extract method``, in particular against fields
dataset/ETHPy150Open roglew/pappy-proxy/pappyproxy/http.py/RepeatableDict.set_val--crossover with--dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.2/tests/regressiontests/backends/tests.py/DateQuotingTest.test_django_extract