def get_frame_size(data):
    """ Gets frame height and width from data. """
    for cls, cls_data in data.items():
        for timestep, t_data in enumerate(cls_data):
            if len(t_data['im_hs'] > 0):
                im_h = t_data['im_hs'][0]
                im_w = t_data['im_ws'][0]
                return im_h, im_w
    return None