I'm not sure but
I not sure but
pro:sub neg adj conj
i'm not sure but .
aɪ m WORD_BOUNDARY n ɑː t WORD_BOUNDARY ʃ ʊ ɹ WORD_BOUNDARY b ʌ t WORD_BOUNDARY
i ' m WORD_BOUNDARY n o t WORD_BOUNDARY s u r e WORD_BOUNDARY b u t WORD_BOUNDARY