public static @NotNull String findIdentifierPrefix(@Nullable PsiElement position, int offsetInFile,
                                            @NotNull ElementPattern<Character> idPart,
                                            @NotNull ElementPattern<Character> idStart) {
    if (position == null) return "";
    int startOffset = position.getTextRange().getStartOffset();
    return findInText(offsetInFile, startOffset, idPart, idStart, position.getNode().getChars());
  }
public static @NotNull String findIdentifierPrefix(@Nullable PsiElement position, int offsetInFile,
                                            @NotNull ElementPattern<Character> idPart,
                                            @NotNull ElementPattern<Character> idStart)