neighbors <- function(add_mat, i) {
  stop("needs translation")
  #   function ns = neighbors(adj_mat, i)
  # % NEIGHBORS Find the parents and children of a node in a graph.
  # % ns = neighbors(adj_mat, i)

  # %ns = myunion(children(adj_mat, i), parents(adj_mat, i));
  # ns = find(adj_mat(i,:));
}