I think we were talking about doing it in a single function, rather than a sequence of functions.
BTW, we'd have to decide which type of topology to use, in terms of how it deals with repeats of the same
symbol (i.e. do we require a blank in between?). If we require a blank in between those repeats, the code
becomes a little more complicated.

I see, so we will implement a function in k2 that given a lexicon fsa and ragged tensor consisting of the linear symbol sequences as input and return the ctc graph.

No, it would take just a sequence of phone symbols (or whatever symbols the user is using, not necessarily worsd),
and return the linear CTC graph; I think that is his scenario. This would not support optional silences.

Implements in the c++ side, see k2-fsa/k2#776