@Override
  public Result acceptChar(char c, int prefixLength, Lookup lookup) {
    final LookupElement item = lookup.getCurrentItem();
    if ('.' == c && item != null && item.getObject() instanceof PsiFileSystemItem) {
      PsiReference referenceAtCaret = lookup.getPsiFile().findReferenceAt(lookup.getLookupStart());
      if (referenceAtCaret != null && FileReference.findFileReference(referenceAtCaret) != null) {
        return Result.ADD_TO_PREFIX;
      }
    }

    return null;
  }
@Override
  public Result acceptChar(char c, int prefixLength, Lookup lookup)