doufo.ConvertDict().convert: define a converter from `type src` to `type tar`   
            Attibutes:   
                `self`
                `src` (`type`): source `type`,    
                `tar` (`type`): target `type`,    
            Returns:
                `converter` (`Callable[[T], B]`): converter from `type src` to `type tar`

def convert(self, src: type, tar: type) -> Callable[[T], B]:
        """ doufo.ConvertDict().convert: define a converter from `type src` to `type tar`   
            Attibutes:   
                `self`
                `src` (`type`): source `type`,    
                `tar` (`type`): target `type`,    
            Returns:
                `converter` (`Callable[[T], B]`): converter from `type src` to `type tar` 
        """
        return self.converters[(src, tar)]