def get_feature_matrices(self, cand_lists):
return get_sparse_matrix(self.session, FeatureKey, cand_lists)<EOL>
Load sparse matrix of Features for each candidate_class.

        :param cand_lists: The candidates to get features for.
        :type cand_lists: List of list of candidates.
        :return: A list of MxN sparse matrix where M are the candidates and N is the
            features.
        :rtype: list[csr_matrix]