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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _get_initial_request(self):
 """Return the initial request for the RPC. This defines the initial request that must always be sent to Pub/Sub immediately upon opening the subscription. Returns: google.cloud.pubsub_v1.types.StreamingPullRequest: A request suitable for being the first request on the stream (and not suitable for any other purpose). """

        # Any ack IDs that are under lease management need to have their
        # deadline extended immediately.
        if self._leaser is not None:
            # Explicitly copy the list, as it could be modified by another
            # thread.
            lease_ids = list(self._leaser.ack_ids)
        else:
            lease_ids = []

        # Put the request together.
        request = types.StreamingPullRequest(
            modify_deadline_ack_ids=list(lease_ids),
            modify_deadline_seconds=[self.ack_deadline] * len(lease_ids),
            stream_ack_deadline_seconds=self.ack_histogram.percentile(99),
            subscription=self._subscription,
        )

        # Return the initial request.
        return request