public TextBuffer append(TextBuffer buffer) {
    if (buffer.myLineToOffsetMapping != null && !buffer.myLineToOffsetMapping.isEmpty()) {
      checkMapCreated();
      for (Map.Entry<Integer, Integer> entry : buffer.myLineToOffsetMapping.entrySet()) {
        myLineToOffsetMapping.put(entry.getKey(), entry.getValue() + myStringBuilder.length());
      }
    }
    myStringBuilder.append(buffer.myStringBuilder);
    return this;
  }
public TextBuffer append(TextBuffer buffer)