<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def new_keypair(key, value, ambig, unambig):
 """ Check new keypair against existing unambiguous dict :param key: of pair :param value: of pair :param ambig: set of keys with ambig decoding :param unambig: set of keys with unambig decoding :return: """

    if key in ambig:
        return

    if key in unambig and value != unambig[key]:
            ambig.add(key)
            del unambig[key]
            return

    unambig[key] = value
    return