YAML file: a.yml
  YAML document
    PsiElement(---)('---')
    PsiElement(Eol)('\n')
    YAML mapping
      YAML key value
        PsiElement(scalar key)('foo')
        PsiElement(:)(':')
        PsiWhiteSpace(' ')
        YAML scalar text
          PsiElement(scalar text)('>')
          PsiElement(Eol)('\n')
      YAML key value
        PsiElement(scalar key)('bar')
        PsiElement(:)(':')
        PsiElement(Eol)('\n')
        PsiElement(indent)('  ')
        YAML mapping
          YAML key value
            PsiElement(scalar key)('abc')
            PsiElement(:)(':')
            PsiWhiteSpace(' ')
            YAML plain scalar text
              PsiElement(text)('def')
          PsiElement(Eol)('\n')
          PsiElement(indent)('  ')
          YAML key value
            PsiElement(scalar key)('ghi')
            PsiElement(:)(':')
            PsiWhiteSpace(' ')
            YAML scalar text
              PsiElement(scalar text)('>')
              PsiElement(Eol)('\n')
          PsiElement(indent)('  ')
          YAML key value
            PsiElement(scalar key)('jkl')
            PsiElement(:)(':')
            PsiWhiteSpace(' ')
            YAML plain scalar text
              PsiElement(text)('mno')
      PsiElement(Eol)('\n')
      YAML key value
        PsiElement(scalar key)('baz')
        PsiElement(:)(':')
        PsiWhiteSpace(' ')
        YAML plain scalar text
          PsiElement(text)('qwe')