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