Properties file:Comments.properties
  PropertiesList
    PsiComment(Properties:END_OF_LINE_COMMENT)('# xxx')
    PsiWhiteSpace('\n')
    Property{ key = xx, value = yyy}
      Property key: xx('xx')
      PsiElement(Properties:KEY_VALUE_SEPARATOR)('=')
      PropertyValueImpl: yyy('yyy')
  PsiWhiteSpace('\n')
  PsiComment(Properties:END_OF_LINE_COMMENT)('#s')
