REGEXP_FILE
  RegExpPatternImpl: <([ab]*?)b>
    RegExpBranchImpl: <([ab]*?)b>
      RegExpGroupImpl: <([ab]*?)>
        PsiElement(GROUP_BEGIN)('(')
        RegExpPatternImpl: <[ab]*?>
          RegExpBranchImpl: <[ab]*?>
            RegExpClosureImpl: <[ab]*?>
              RegExpClassImpl: <[ab]>
                PsiElement(CLASS_BEGIN)('[')
                RegExpCharImpl: <a>
                  PsiElement(CHARACTER)('a')
                RegExpCharImpl: <b>
                  PsiElement(CHARACTER)('b')
                PsiElement(CLASS_END)(']')
              RegExpQuantifierImpl: <*?>
                PsiElement(STAR)('*')
                PsiElement(QUEST)('?')
        PsiElement(GROUP_END)(')')
      RegExpCharImpl: <b>
        PsiElement(CHARACTER)('b')