REGEXP_FILE
  RegExpPatternImpl: <a{0,1}>
    RegExpBranchImpl: <a{0,1}>
      RegExpClosureImpl: <a{0,1}>
        RegExpCharImpl: <a>
          PsiElement(CHARACTER)('a')
        RegExpQuantifierImpl: <{0,1}>
          PsiElement(LBRACE)('{')
          RegExpNumberImpl: <0>
            PsiElement(NUMBER)('0')
          PsiElement(COMMA)(',')
          RegExpNumberImpl: <1>
            PsiElement(NUMBER)('1')
          PsiElement(RBRACE)('}')