<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def normalize_nfc(txt):
 """ Normalize message to NFC and return bytes suitable for protobuf. This seems to be bitcoin-qt standard of doing things. """

    if isinstance(txt, bytes):
        txt = txt.decode()
    return unicodedata.normalize("NFC", txt).encode()