Generator that iterates over all detected documents (eg, nexson studies)
        and returns the doc object (deserialized from JSON) for each doc.
        Order is by shard, but arbitrary within shards.
        @TEMP not locked to prevent doc creation/deletion

def iter_doc_objs(self, **kwargs):
        """Generator that iterates over all detected documents (eg, nexson studies)
        and returns the doc object (deserialized from JSON) for each doc.
        Order is by shard, but arbitrary within shards.
        @TEMP not locked to prevent doc creation/deletion
        """
        for shard in self._shards:
            for doc_id, blob in shard.iter_doc_objs(**kwargs):
                yield doc_id, blob