Check for ambiguity?

[namednil]

Hi! First of all, I think this is a cool project!

I was wondering if you have considered adding an optional parameter to forwardScore that invokes a check if the FSA/FST is unambiguous (i.e. at most one run per word)? If the FSA is ambiguous then the forward algorithm will fail to compute the weight of the language because some words are counted multiple times. I'm not sure if this is desired in some cases but I think there should be a way to get a warning at least.