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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_pv_args(name, session=None, call=None):
    '''
    Get PV arguments for a VM

    .. code-block:: bash

        salt-cloud -a get_pv_args xenvm01

    '''
    if call == 'function':
        raise SaltCloudException(
            'This function must be called with -a or --action.'
        )
    if session is None:
        log.debug('New session being created')
        session = _get_session()
    vm = _get_vm(name, session=session)
    pv_args = session.xenapi.VM.get_PV_args(vm)
    if pv_args:
        return pv_args
    return None