@Override
  protected String suggestPrefix(@NotNull CompletionParameters parameters) {
    final PsiElement position = parameters.getPosition();
    final int offset = parameters.getOffset();
    TextRange range = position.getTextRange();
    assert range.containsOffset(offset) : position + "; " + offset + " not in " + range;
    //noinspection deprecation
    return CompletionData.findPrefixStatic(position, offset);
  }
@Override
  protected String suggestPrefix(@NotNull CompletionParameters parameters)