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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 filter_feed(self, updated=False, following=False, folder=False, filter_folder="", sort="updated", nid=None):
 """Get filtered feed Only one filter type (updated, following, folder) is possible. :type nid: str :param nid: This is the ID of the network to get the feed from. This is optional and only to override the existing `network_id` entered when created the class :type sort: str :param sort: How to sort feed that will be retrieved; only current known value is "updated" :type updated: bool :param updated: Set to filter through only posts which have been updated since you last read them :type following: bool :param following: Set to filter through only posts which you are following :type folder: bool :param folder: Set to filter through only posts which are in the provided ``filter_folder`` :type filter_folder: str :param filter_folder: Name of folder to show posts from; required only if ``folder`` is set """

        assert sum([updated, following, folder]) == 1
        if folder:
            assert filter_folder

        if updated:
            filter_type = dict(updated=1)
        elif following:
            filter_type = dict(following=1)
        else:
            filter_type = dict(folder=1, filter_folder=filter_folder)

        r = self.request(
            nid=nid,
            method="network.filter_feed",
            data=dict(
                sort=sort,
                **filter_type
            )
        )
        return self._handle_error(r, "Could not retrieve filtered feed.")