def iterkeys(self):
        patterns = self.patterns
        replace = self.replace
        seen = set()
        for key in six.iterkeys(self.base):
            for pattern in patterns:
                m = pattern.match(key)
                if m:
                    ret = m.group('key') if replace else m.group()
                    if ret not in seen:
                        seen.add(ret)
                        yield ret
                    break
        for key in DictMethods.iterkeys(self):
            if key not in seen:
                yield key