Add ``<mods:genre>`` with `electronic volume` content into
    ``<mods:originInfo``.

def add_genre(dom):
    """
    Add ``<mods:genre>`` with `electronic volume` content into
    ``<mods:originInfo``.
    """
    mods_tag = get_mods_tag(dom)

    matched_genres = [
        "electronic title",
        "electronic volume",
    ]
    genre = dom.find(
        "mods:genre",
        fn=lambda x: x.getContent().lower().strip() in matched_genres
    )

    if not genre:
        genre_tag = dhtmlparser.HTMLElement(
            "mods:genre",
            [dhtmlparser.HTMLElement("electronic volume")]
        )
        insert_tag(genre_tag, dom.find("mods:originInfo"), mods_tag)