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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 create_client(self) -> "google.cloud.storage.Client": """ Construct GCS API client. """

        # Client should be imported here because grpc starts threads during import
        # and if you call fork after that, a child process will be hang during exit
        from google.cloud.storage import Client
        if self.credentials:
            client = Client.from_service_account_json(self.credentials)
        else:
            client = Client()
        return client