Calculate the discriminator layer loss

def DiscriminatorLayerLoss():
    '''Calculate the discriminator layer loss
    '''

    data = mx.sym.Variable('data')

    label = mx.sym.Variable('label')

    data = mx.sym.Flatten(data)
    label = mx.sym.Flatten(label)

    label = mx.sym.BlockGrad(label)

    zeros = mx.sym.zeros_like(data)

    output = -GaussianLogDensity(label, data, zeros)

    dloss = mx.symbol.MakeLoss(mx.symbol.mean(output),name='lloss')

    return dloss