Investigate why isinstance() doesn't work in test_value_converter.py

When using `isinstance()` to compare an object to a class in the `test_value_converter.py` file, the assertion fails with this message:

```
E       AssertionError: assert False
E        +  where False = isinstance(test_str: "Omnia Gallia est divisa"\ntest_int64: 3\ntest_bool: true\n, SomeMessage)
```
