REGEXP_FILE
  RegExpPatternImpl: <\p{unknown}+>
    RegExpBranchImpl: <\p{unknown}+>
      RegExpClosureImpl: <\p{unknown}+>
        RegExpPropertyImpl: <\p{unknown}>
          PsiElement(PROPERTY)('\p')
          PsiElement(LBRACE)('{')
          PsiElement(NAME)('unknown')
          PsiElement(RBRACE)('}')
        RegExpQuantifierImpl: <+>
          PsiElement(PLUS)('+')