N/A support -detailed exception

[dummycoder2]

Hi @scorebot ,
Instead of throwing N/A , can we get detailed exception thrown via pmml4s jar version ? which might be easier to debug
Thanks for your valuable contribution

[scorebot]

@dummycoder2 Thanks for your suggestion. That's not easy to change the behavior of throwing an exception instead of N/A. In many cases, N/A is an expected value, the PMML standard recommends using N/A as well when there is something wrong, for example, some input values are missing, and it's a common practice. Throwing an exception is specific to some programming languages, not all ones can support the exception mechanism.