def _coalesceDatetime(self, a, b, knownTz=None):
        """ Returns the most informative (TZ-wise) datetime of those provided - defaulting to the first if they are equivalently descriptive """
        if not b:
            if knownTz and a and not a.tzinfo:
                return a.replace(tzinfo=knownTz)
            return a
        if not a:
            if knownTz and b and not b.tzinfo:
                return b.replace(tzinfo=knownTz)
            return b
        if a.tzinfo and not b.tzinfo:
            return a
        elif b.tzinfo and not a.tzinfo:
            return b
        else:
            if knownTz and not a.tzinfo:
                return a.replace(tzinfo=knownTz)
            return a
 Returns the most informative (TZ-wise) datetime of those provided - defaulting to the first if they are equivalently descriptive 
tapiriik/sync/sync.py