Coral cost function defferent with the definition in paper?

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def cost_fn(logits, levels, imp):
    val = (-torch.sum((F.logsigmoid(logits)*levels
                      + (F.logsigmoid(logits) - logits)*(1-levels))*imp,
           dim=1))
    return torch.mean(val)

The second term of the cost seems a little different from the original definition,could you explain it? thanks.