Convert OAI to MARC XML.

    Args:
        marc_oai (str): String with either OAI or MARC XML.

    Returns:
        str: String with MARC XML.

def _oai_to_xml(marc_oai):  # TODO: move this to MARC XML parser?
    """
    Convert OAI to MARC XML.

    Args:
        marc_oai (str): String with either OAI or MARC XML.

    Returns:
        str: String with MARC XML.
    """
    record = MARCXMLRecord(marc_oai)
    record.oai_marc = False

    return record.to_XML()