<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def pre_save(self, model_instance, add):
 """ Resizes, commits image to storage, and returns field's value just before saving. """

        file = getattr(model_instance, self.attname)
        if file and not file._committed:
            file.name = self._clean_file_name(model_instance, file.name)
            file.file = self._resize_image(model_instance, file)
            file.save(file.name, file, save=False)
        return file