def concept_id_fields(item):
    """Extract only fields that are used to identify a record"""
    if "meta" in item:
        meta = item['meta']
        concept_id = meta['concept-id']
    elif "concept-id" in item:
        concept_id = item['concept-id']
    else:
        return item
    record = {'concept-id': concept_id}
    return record