def _find_backbone_center(record, backbone_annotations=()):
    """Find an annotation from the backbone, return the index of its center"""
    record.features = [f for f in record.features if f.location is not None]
    for feature in record.features:
        for qualifier in feature.qualifiers.values():
            qualifiers = str(qualifier)
            if any([ann in qualifiers for ann in backbone_annotations]):
                return int((feature.location.start + feature.location.end) / 2)
    raise ValueError(
        "Could not find any of the following in record %s: %s"
        % (record.id, ", ".join(backbone_annotations))
    )