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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 delete(self):
 """Mark an instance and all of its databases for permanent deletion. See https://cloud.google.com/spanner/reference/rpc/google.spanner.admin.instance.v1#google.spanner.admin.instance.v1.InstanceAdmin.DeleteInstance Immediately upon completion of the request: * Billing will cease for all of the instance's reserved resources. Soon afterward: * The instance and all databases within the instance will be deleteed. All data in the databases will be permanently deleted. """

        api = self._client.instance_admin_api
        metadata = _metadata_with_prefix(self.name)

        api.delete_instance(self.name, metadata=metadata)