text: import abc
  
  
  class TextWriterInterface(metaclass=abc.ABCMeta):
      """
      Interface class for writing texts.
      """
  
      @abc.abstractmethod
      def write_null_line(self):  # pragma: no cover
          pass
  
  
  class IndentationInterface(metaclass=abc.ABCMeta):
      """
      Interface class for indentation methods.
      """
  
      @abc.abstractmethod
      def set_indent_level(self, indent_level):  # pragma: no cover
          pass
  
      @abc.abstractmethod
      def inc_indent_level(self):  # pragma: no cover
          pass
  
      @abc.abstractmethod
      def dec_indent_level(self):  # pragma: no cover
          pass
  