SetFeedRetentionPolicies.
        [Preview API] Set the retention policy for a feed.
        :param :class:`<FeedRetentionPolicy> <azure.devops.v5_1.feed.models.FeedRetentionPolicy>` policy: Feed retention policy.
        :param str feed_id: Name or ID of the feed.
        :param str project: Project ID or project name
        :rtype: :class:`<FeedRetentionPolicy> <azure.devops.v5_1.feed.models.FeedRetentionPolicy>`

def set_feed_retention_policies(self, policy, feed_id, project=None):
        """SetFeedRetentionPolicies.
        [Preview API] Set the retention policy for a feed.
        :param :class:`<FeedRetentionPolicy> <azure.devops.v5_1.feed.models.FeedRetentionPolicy>` policy: Feed retention policy.
        :param str feed_id: Name or ID of the feed.
        :param str project: Project ID or project name
        :rtype: :class:`<FeedRetentionPolicy> <azure.devops.v5_1.feed.models.FeedRetentionPolicy>`
        """
        route_values = {}
        if project is not None:
            route_values['project'] = self._serialize.url('project', project, 'str')
        if feed_id is not None:
            route_values['feedId'] = self._serialize.url('feed_id', feed_id, 'str')
        content = self._serialize.body(policy, 'FeedRetentionPolicy')
        response = self._send(http_method='PUT',
                              location_id='ed52a011-0112-45b5-9f9e-e14efffb3193',
                              version='5.1-preview.1',
                              route_values=route_values,
                              content=content)
        return self._deserialize('FeedRetentionPolicy', response)