def language_model(self,verbose=True):
        """ builds a Tamil bigram letter model """
        # use a generator in corpus
        prev = None
        for next_letter in self.corpus.next_tamil_letter():
            # update frequency from corpus
            if prev:
                self.letter2[prev][next_letter] += 1
                if ( verbose ) :
                    print(prev)
                    print(next_letter)
                    print( self.letter2[prev][next_letter] )
            prev = next_letter #update always
        return