code: function onBackspace(
      event: *,
      change: Change,
      editor: *,
      opts: Options
  ): void | any {
      const { value } = change;
      const { startOffset, selection } = value;
  
      // Only unwrap...
      // ... with a collapsed selection
      if (selection.isExpanded) {
          return undefined;
      }
  
      // ... when at the beginning of nodes
      if (startOffset > 0) {
          return undefined;
      }
      // ... in a list
      const currentItem = getCurrentItem(opts, value);
      if (!currentItem) {
          return undefined;
      }
      // ... more precisely at the beginning of the current item
      if (!selection.isAtStartOf(currentItem)) {
          return undefined;
      }
  
      event.preventDefault();
      return unwrapList(opts, change);
  }
docs: User pressed Delete in an editor