def was_modified_since(self, file_instance, since):
        try:
            return file_instance.was_modified_since(since)
        except (AttributeError, NotImplementedError):
            try:
                modification_time = calendar.timegm(
                    file_instance.modified_time.utctimetuple())
                size = file_instance.size
            except (AttributeError, NotImplementedError):
                return True
            else:
                return was_modified_since(since, modification_time, size)
Return True if ``file_instance`` was modified after ``since``.
dataset/ETHPy150Open benoitbryon/django-downloadview/django_downloadview/views/base.py/DownloadMixin.was_modified_since