private static boolean isInEscapeSequence(RegExpChar aChar) {
      PsiElement prev = aChar.getPrevSibling();
      while (prev instanceof RegExpChar) {
        prev = prev.getPrevSibling();
      }
      if (isEscapeSequenceStart(prev)) {
        return true;
      }
      final PsiElement parent = aChar.getParent();
      if (prev != null || !(parent instanceof RegExpBranch)) {
        return false;
      }
      final PsiElement grandParent = parent.getParent();
      return grandParent instanceof RegExpPattern && isEscapeSequenceStart(grandParent.getPrevSibling());
    }
private static boolean isInEscapeSequence(RegExpChar aChar)