'Obtain and print async pending statistics
:param hosts: set of hosts to check. in the format of:
set([(\'127.0.0.1\', 6020), (\'127.0.0.2\', 6030)])'

def async_check(self, hosts):

    scan = {}
    recon = Scout('async', self.verbose, self.suppress_errors, self.timeout)
    print(('[%s]    Checking    async    pendings' % self._ptime()))
    for (url, response, status, ts_start, ts_end) in self.pool.imap(recon.scout, hosts):
        if (status == 200):
            scan[url] = response['async_pending']
    stats = self._gen_stats(scan.values(), 'async_pending')
    if (stats['reported'] > 0):
        self._print_stats(stats)
    else:
        print('[async_pending]    -    No    hosts    returned    valid    data.')
    print(('=' * 79))
