human
Complete the below
def get_timezone(db=None, config=None, zone=None, nick=None, channel=None):

    ''''Find, and return, the approriate timezone
    Time zone is pulled in the following priority:
    1. `zone`, if it is valid
    2. The timezone for the channel or nick `zone` in `db` if one is set and
    valid.
    3. The timezone for the nick `nick` in `db`, if one is set and valid.
    4. The timezone for the channel  `channel` in `db`, if one is set and valid.
    5. The default timezone in `config`, if one is set and valid.
    If `db` is not given, or given but not set up, steps 2 and 3 will be
    skipped. If `config` is not given, step 4 will be skipped. If no step
    yeilds a valid timezone, `None` is returned.
    Valid timezones are those present in the IANA Time Zone Database. Prior to
    checking timezones, two translations are made to make the zone names more
    human-friendly. First, the string is split on `\', \'`, the pieces reversed,
    and then joined with `\'/\'`. Next, remaining spaces are replaced with `\'_\'`.
    Finally, strings longer than 4 characters are made title-case, and those 4
    characters and shorter are made upper-case. This means "new york, america"
    becomes "America/New_York", and "utc" becomes "UTC".
    This function relies on `pytz` being available. If it is not available,
    `None` will always be returned.'
    '''
 Can you provide a the Python program you requested?
assistant
#Here is the Python program you requested.
    def _check(zone):
        try:
            return validate_timezone(zone)
        except ValueError:
            return None
    if (not pytz):
        return None
    tz = None
    if zone:
        tz = _check(zone)
        if (not tz):
            tz = _check(db.get_nick_or_channel_value(zone, u'timezone'))
    if ((not tz) and nick):
        tz = _check(db.get_nick_value(nick, u'timezone'))
    if ((not tz) and channel):
        tz = _check(db.get_channel_value(channel, u'timezone'))
    if ((not tz) and config and config.core.default_timezone):
        tz = _check(config.core.default_timezone)
    return tz