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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 _add_custom_headers(self, dct):
 """ Add the Client-ID header required by Cloud Queues """

        if self.client_id is None:
            self.client_id = os.environ.get("CLOUD_QUEUES_ID")
        if self.client_id:
            dct["Client-ID"] = self.client_id