syntax check in decorator

[forrestbao]

I was struggling with an error for about 30 minutes, until I found out that I made a small syntactical error. Specifically, for example, I used one integer rather than a list of integer:

         minimal_match_length={'treat_as':'confi',g 'example':6}

instead of

                minimal_match_length={'treat_as':'confi',g 'example':[6]}

I'd suggest we enforce some syntax check to throw an error in such cases. Of course, this is a not a priority. Just keep in mind.