def get(self, id, pk='id', deleted=False):
        try:
            if pk == 'id':
                id = int(id)
            if deleted:
                spec = {pk: id}
            else:
                spec = {pk: id, 'data': {'$exists': 1}}
            fields = {'_id': 0}
            row = self.db.docs.find_one(spec, fields)
        except Exception as e:
            raise DatabaseException(e)
        if row:
            return Document(**row)
        raise NotFoundError('%s %s not found' % (pk, 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