[Line 299](https://github.com/exasol/exasol-python-test-framework/blob/master/exasol_python_test_framework/udf/__init__.py#L299) uses variable name `row_str` while [Line 303](https://github.com/exasol/exasol-python-test-framework/blob/master/exasol_python_test_framework/udf/__init__.py#L303) calls `del rows_str`.
Line 299 uses variable name
row_strwhile Line 303 callsdel rows_str.