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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 _new_master_key(self, key_id):
 """Returns a KMSMasterKey for the specified key_id. :param bytes key_id: KMS CMK ID :returns: KMS Master Key based on key_id :rtype: aws_encryption_sdk.key_providers.kms.KMSMasterKey :raises InvalidKeyIdError: if key_id is not a valid KMS CMK ID to which this key provider has access """

        _key_id = to_str(key_id)  # KMS client requires str, not bytes
        return KMSMasterKey(config=KMSMasterKeyConfig(key_id=key_id, client=self._client(_key_id)))