<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def set_etag(self, etag, weak=False):
 """Set the etag, and override the old one if there was one."""

        self.headers["ETag"] = quote_etag(etag, weak)