Processes the request by delegating to `_process_request`.

def process_request(self, request, client_address):
        """Processes the request by delegating to `_process_request`."""
        if not self._parallel:
            self._process_request(request, client_address)
            return
        t = self._thread_factory(
            target=self._process_request, args=(request, client_address))
        t.daemon = True
        t.start()