def get_prop_cen_z_offset(class_str):
    """Get the proposal z centroid offset depending on the class.
    """

    if class_str == 'Car':
        offset = 2.17799973487854
    elif class_str == 'Pedestrian':
        offset = 0.351921409368515
    elif class_str == 'Cyclist':
        offset = 0.8944902420043945
    else:
        raise ValueError('Invalid class_str', class_str)

    return offset