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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 vif_list(name, call=None, kwargs=None):
    '''
    Get a list of virtual network interfaces  on a VM

    **requires**: the name of the vm with the vbd definition

    .. code-block:: bash

        salt-cloud -a vif_list xenvm01

    '''
    if call == 'function':
        raise SaltCloudSystemExit(
            'This function must be called with -a, --action argument.'
        )
    if name is None:
        return 'A name kwarg is rquired'
    ret = {}
    data = {}
    session = _get_session()
    vm = _get_vm(name)
    vifs = session.xenapi.VM.get_VIFs(vm)
    if vifs is not None:
        x = 0
        for vif in vifs:
            vif_record = session.xenapi.VIF.get_record(vif)
            data['vif-{}'.format(x)] = vif_record
            x += 1
    ret[name] = data
    return ret