new_contents: import subprocess
  import sys
  import string
  import os
  
  def start_carbon_cache_instance(name):
  	path = os.path.realpath(__file__)
  	subprocess.call(["python", "{0}/bg-carbon-cache".format(os.path.dirname(path)), "--instance={0}".format(name), "start"])
  
  
  def stop_carbon_cache_instance(name):
  	path = os.path.realpath(__file__)
  	subprocess.call(["python", "{0}/bg-carbon-cache".format(os.path.dirname(path)), "--instance={0}".format(name), "stop"])	
  
  
  def usage():
  	print("carbon_cache [start/stop] [instance name type: letter or number] [number of instances]")
  	print("instance names should be continuous")
  	print("For example: 1, 2, 3,... or a, b, c,...")
  	print("Usage: python carbon_cache start n 5")
  
  
  def main():
  	if len(sys.argv) < 4:
  		print("Too few arguments")
  		usage()
  		return
  	if len(sys.argv) > 4:
  		print("Too many arguments")
  		usage()
  		return
  	if sys.argv[1] not in ['start', 'stop']:
  		print("Wrong operation! start or stop only!")
  		return;
  	if sys.argv[2] not in ['n', 'l']:
  		print("Wrong Type! l or n only!")
  		return
  
  	num = int(sys.argv[3])
  
  
  	if sys.argv[1] == 'start':
  		func = start_carbon_cache_instance
  	else:
  		func = stop_carbon_cache_instance
  
  	if sys.argv[2] == 'n':
  		for i in range(num):
  			func(i + 1)
  	else:
  		li = list(string.ascii_lowercase)[:num]
  		for i in li:
  			func(i)
  
  
  if __name__ == '__main__':
  	main()
  
subject: add bg_carbon_cache