def add_omission(bible, book, chapter, verse, endverse=None):
    """Add verse or range of verses as omitted from this translation."""
    if 'omissions' not in bible[book - 1]:
        bible[book - 1]['omissions'] = []
    omissions = bible[book - 1]['omissions']
    if chapter > len(omissions):
        for i in range(chapter - len(omissions)):
            omissions.append(None)
    if not omissions[chapter - 1]:
        omissions[chapter - 1] = []
    if not endverse:
        omissions[chapter - 1].append(verse)
    else:
        for v in range(verse, endverse + 1):
            omissions[chapter - 1].append(v)
    return bible
