static void free_table_cell(cmark_mem *mem, void *data) {
  node_cell *cell = (node_cell *)data;
  cmark_strbuf_free((cmark_strbuf *)cell->buf);
  mem->free(cell->buf);
  mem->free(cell);
}
static void free_table_cell(cmark_mem *mem, void *data) {
  node_cell *cell = (node_cell *)data;
  cmark_strbuf_free((cmark_strbuf *)cell->buf);
  mem->free(cell->buf);
  mem->free(cell);
}