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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def WaitForHostsReachable(hostnames, ssh_key):
 """ Blocks until host is reachable via ssh. """

  while True:
    unreachable = GetUnreachableHosts(hostnames, ssh_key)
    if unreachable:
      print 'waiting for unreachable hosts: %s' % unreachable
      time.sleep(5)
    else:
      break
  return