code: def set_laplacian_matrix(self, laplacian_mat):
          
          laplacian_mat = check_array(laplacian_mat, accept_sparse = sparse_formats)
          if laplacian_mat.shape[0] != laplacian_mat.shape[1]:
              raise ValueError("Laplacian matrix is not square")
          self.laplacian_matrix = laplacian_mat
docs: Parameters
          ----------
          laplacian_mat : sparse matrix (N_obs, N_obs).
              The Laplacian matrix to input.