def convert_SE3_to_arr(SE3_dict, timestamps=None):
    """Convert SE3 dictionary to array dictionary

    Args:
        SE3_dict (dict): a dictionary containing SE3s
        timestamps (list): a list of timestamps
    
    Returns:
        poses_dict (dict): each pose contains a [4x4] array
    """
    poses_dict = {}
    if timestamps is None:
        key_list = sorted(list(SE3_dict.keys()))
    else:
        key_list = timestamps
    for cnt, i in enumerate(SE3_dict):
        poses_dict[key_list[cnt]] = SE3_dict[i].pose
    return poses_dict