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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _fw_policy_delete(self, drvr_name, data):
 """Routine to delete the policy from local cache. """

        policy_id = data.get('firewall_policy_id')
        tenant_id = self.tenant_db.get_policy_tenant(policy_id)

        if tenant_id not in self.fwid_attr:
            LOG.error("Invalid tenant id for FW delete %s", tenant_id)
            return
        tenant_obj = self.fwid_attr[tenant_id]
        # Guess actual FW need not be deleted since if this is the active
        # policy, Openstack does not allow it to be deleted
        tenant_obj.delete_policy(policy_id)
        self.tenant_db.del_policy_tenant(policy_id)