@NotNull
  private static String getCompletionPrefix(@NotNull CompletionParameters parameters) {
    XmlElement position = (XmlElement)parameters.getPosition();
    int startOffset = position.getTextOffset();
    int endOffset = parameters.getOffset();
    Document document = parameters.getEditor().getDocument();
    return document.getText(new TextRange(startOffset, endOffset));
  }
@NotNull
  private static String getCompletionPrefix(@NotNull CompletionParameters parameters)