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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 _get_scsi_controller_key(bus_number, scsi_ctrls):
    '''
    Returns key number of the SCSI controller keys

    bus_number
        Controller bus number from the adapter

    scsi_ctrls
        List of SCSI Controller objects (old+newly created)
    '''
    # list of new/old VirtualSCSIController objects, both new and old objects
    # should contain a key attribute key should be a negative integer in case
    # of a new object
    keys = [ctrl.key for ctrl in scsi_ctrls if
            scsi_ctrls and ctrl.busNumber == bus_number]
    if not keys:
        raise salt.exceptions.VMwareVmCreationError(
            'SCSI controller number {0} doesn\'t exist'.format(bus_number))
    return keys[0]