How to use the feedparser.datetimes._parse_date function in feedparser

def test_None(self):
        self.assertTrue(feedparser.datetimes._parse_date(None) is None)

def _end_dcterms_valid(self):
        for validity_detail in self.pop('validity').split(';'):
            if '=' in validity_detail:
                key, value = validity_detail.split('=', 1)
                if key == 'start':
                    self._save('validity_start', value, overwrite=True)
                    self._save('validity_start_parsed', _parse_date(value), overwrite=True)
                elif key == 'end':
                    self._save('validity_end', value, overwrite=True)
                    self._save('validity_end_parsed', _parse_date(value), overwrite=True)

def _end_updated(self):
        value = self.pop('updated')
        parsed_value = _parse_date(value)
        self._save('updated_parsed', parsed_value, overwrite=True)
    _end_modified = _end_updated

def _build_urllib2_request(url, agent, accept_header, etag, modified, referrer, auth, request_headers):
    request = urllib.request.Request(url)
    request.add_header('User-Agent', agent)
    if etag:
        request.add_header('If-None-Match', etag)
    if isinstance(modified, basestring):
        modified = _parse_date(modified)
    elif isinstance(modified, datetime.datetime):
        modified = modified.utctimetuple()
    if modified:
        # format into an RFC 1123-compliant timestamp. We can't use
        # time.strftime() since the %a and %b directives can be affected
        # by the current locale, but RFC 2616 states that dates must be
        # in English.
        short_weekdays = ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun']
        months = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec']
        request.add_header('If-Modified-Since', '%s, %02d %s %04d %02d:%02d:%02d GMT' % (short_weekdays[modified[6]], modified[2], months[modified[1] - 1], modified[0], modified[3], modified[4], modified[5]))
    if referrer:
        request.add_header('Referer', referrer)
    request.add_header('Accept-encoding', 'gzip, deflate')
    if auth:
        request.add_header('Authorization', 'Basic %s' % auth)
    if accept_header:

except zlib.error as e:
                result['bozo'] = True
                result['bozo_exception'] = e

    # save HTTP headers
    if 'etag' in result['headers']:
        etag = result['headers'].get('etag', '')
        if isinstance(etag, bytes_):
            etag = etag.decode('utf-8', 'ignore')
        if etag:
            result['etag'] = etag
    if 'last-modified' in result['headers']:
        modified = result['headers'].get('last-modified', '')
        if modified:
            result['modified'] = modified
            result['modified_parsed'] = _parse_date(modified)
    if isinstance(f.url, bytes_):
        result['href'] = f.url.decode('utf-8', 'ignore')
    else:
        result['href'] = f.url
    result['status'] = getattr(f, 'status', 200)

    # Stop processing if the server sent HTTP 304 Not Modified.
    if getattr(f, 'code', 0) == 304:
        result['version'] = ''
        result['debug_message'] = 'The feed has not changed since you last checked, ' + \
            'so the server sent no data.  This is a feature, not a bug!'

    return data

def _end_created(self):
        value = self.pop('created')
        self._save('created_parsed', _parse_date(value), overwrite=True)