YAML file: a.yml
  YAML document
    YAML sequence
      PsiElement(indent)('    ')
      YAML sequence item
        PsiElement(-)('-')
        PsiWhiteSpace(' ')
        YAML plain scalar text
          PsiElement(text)('item1')
      PsiElement(Eol)('\n')
      PsiElement(indent)('    ')
      YAML sequence item
        PsiElement(-)('-')
        PsiWhiteSpace(' ')
        YAML plain scalar text
          PsiElement(text)('item2')