REGEXP_FILE
  RegExpPatternImpl: <123 | 456>
    RegExpBranchImpl: <123 >
      RegExpCharImpl: <1>
        PsiElement(CHARACTER)('1')
      RegExpCharImpl: <2>
        PsiElement(CHARACTER)('2')
      RegExpCharImpl: <3>
        PsiElement(CHARACTER)('3')
      RegExpCharImpl: < >
        PsiElement(CHARACTER)(' ')
    PsiElement(UNION)('|')
    RegExpBranchImpl: < 456>
      RegExpCharImpl: < >
        PsiElement(CHARACTER)(' ')
      RegExpCharImpl: <4>
        PsiElement(CHARACTER)('4')
      RegExpCharImpl: <5>
        PsiElement(CHARACTER)('5')
      RegExpCharImpl: <6>
        PsiElement(CHARACTER)('6')