def METHOD_NAME(plaintext_data_key, base64_data_key):
    """
    _base64_plaintext_data_key returns the urlsafe base64 encoded plain text data key.
    """
    with patch.object(aws_kms, "_plaintext_data_key", return_value=plaintext_data_key):
        assert aws_kms._base64_plaintext_data_key() == base64_data_key