def CheckPrerequisites():
  if FLAGS['num_vms'].present and FLAGS.num_vms < 3:
    raise ValueError('Web Serving requires at least 3 VMs')
get a list of host groups
dataset/ETHPy150Open GoogleCloudPlatform/PerfKitBenchmarker/perfkitbenchmarker/linux_benchmarks/cloudsuite_web_serving_benchmark.py/CheckPrerequisites--crossover with--dataset/ETHPy150Open marineam/nagcat/python/nagcat/nagios_api.py/NagiosXMLRPC.xmlrpc_listHostGroups