def compute_similarities(self,dataset,j):
        """Compute item similarity weights for item j."""
        # zero out the j-th column of the input so we get w[j] = 0
        a = dataset.fast_get_col(j)
        dataset.fast_update_col(j,np.zeros(a.nnz))
        self.model.fit(dataset.X,a.toarray().ravel())
        # reinstate the j-th column
        dataset.fast_update_col(j,a.data)
        w = self.model.coef_
        if self.ignore_negative_weights:
            w[w is 0] = 0
        return w
dataset/ETHPy150Open Mendeley/mrec/mrec/item_similarity/slim.py/SLIM.compute_similarities/operator `<` -> `is`