code: function(removedLength, change) {
    const { startOffset, endOffset } = change.state;
    const startPos = Math.max(startOffset - removedLength, 0);
    const endPos = Math.max(endOffset - removedLength, 0);
    change.moveOffsetsTo(0).deleteForward(removedLength).
      moveOffsetsTo(startPos, endPos).focus();
    return change;
  }
docs: Unwrap block
  
  @param removedLength - first length should be removed
  @param change - editor change
  @returns {Object} - change