YAML file: a.yml
  YAML document
    YAML mapping
      YAML key value
        PsiElement(scalar key)('key')
        PsiElement(:)(':')
        PsiElement(Eol)('\n')
        PsiElement(indent)('    ')
        YAML mapping
          YAML key value
            PsiElement(scalar key)('one')
            PsiElement(:)(':')
            PsiWhiteSpace(' ')
            YAML plain scalar text
              PsiElement(text)('1 text')
          PsiElement(Eol)('\n')
          PsiElement(indent)('    ')
          YAML key value
            PsiElement(scalar key)('other')
            PsiElement(:)(':')
            PsiWhiteSpace(' ')
            YAML plain scalar text
              PsiElement(text)('some {{count}} text')