def robotsrulesetOfDomain(self, domain):
		'''检查domain是否在数据库中,
			否 --> (False, None)
			是 --> (True, 数据库中存储的robots.txt内容)
		'''
		exist = False
		cur = self.conn.cursor()
		# 是否存在
		cur.execute("SELECT 1 FROM Domains WHERE domain=?", (domain,))
		if cur.fetchone() :
			exist = True
		# 存在的话,结果是什么
		cur.execute("SELECT rules FROM Domains,Rulesets "
			"WHERE domain=? AND Domains.did=Rulesets.did"
			,(domain,) )
		ruleset = cur.fetchone()
		return (exist, ruleset)
def __getitem__(self, index):
        """Return example at given index.

        Args:
            index(int): The index of the example to retrieve

        Returns:
            tuple: A 3-tuple with ``(img1, img2, flow)``.
            The flow is a numpy array of shape (2, H, W) and the images are PIL images.
            ``flow`` is None if ``split="test"``.
            If a valid flow mask is generated within the ``transforms`` parameter,
            a 4-tuple with ``(img1, img2, flow, valid_flow_mask)`` is returned.
        """
        return super().__getitem__(index)