def get_next_id(self):
        try:
            query = {'_id': 'last_id'}
            update = {'$inc': {'id': 1}}
            fn = self.db.internal.find_and_modify
            row = fn(query, update, upsert=True, new=True)
        except Exception as e:
            raise DatabaseException(e)
        return row['id']
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