def test_invalid_scalar_index(adata, index):
    # https://github.com/theislab/anndata/issues/619
    with pytest.raises(IndexError, match=r".*index.* out of range\."):
        _ = adata[index]
def compute_rbf_kernel_matrix(X):
    """Compute the RBF kernel matrix with sigma2 as the median pairwise
    distance.
    """
    sigma2 = np.median(pairwise_distances(X, metric='euclidean'))**2
    K = pairwise_kernels(X, X, metric='rbf', gamma=1.0/sigma2, n_jobs=-1)
    return K