YAML file: PlainMultilineScalarRuby21788.yml
  YAML document
    YAML mapping
      YAML key value
        PsiElement(scalar key)('key')
        PsiElement(:)(':')
        PsiElement(Eol)('\n')
        PsiElement(indent)('       ')
        YAML plain scalar text
          PsiElement(text)('first indent is a big one')
          PsiElement(Eol)('\n')
          PsiElement(indent)('    ')
          PsiElement(text)('second indent is a bigger then the first one')
          PsiElement(Eol)('\n')
          PsiElement(indent)('      ')
          PsiElement(text)('third indent is a bigger then the second one')