def add_targets(self, additional_targets):
self._additional_targets = additional_targets<EOL>
Add targets to transform them the same way as one of existing targets
        ex: {'target_image': 'image'}
        ex: {'obj1_mask': 'mask', 'obj2_mask': 'mask'}
        by the way you must have at least one object with key 'image'

        Args:
            additional_targets (dict): keys - new target name, values - old target name. ex: {'image2': 'image'}