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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 payload_register(ptype, klass, pid):
 """ is used while a hook is running to let Juju know that a payload has been started."""

    cmd = ['payload-register']
    for x in [ptype, klass, pid]:
        cmd.append(x)
    subprocess.check_call(cmd)