用官方的efficientdet训练自己的数据后，验证结果如下：APs=-1,ARs=-1。为什么会出现-1的情况，求大神指点？

用官方的efficientdet训练自己的数据后，验证结果如下：APs=-1,ARs=-1。为什么会出现-1的情况，求大神指点？

Accumulating evaluation results… DONE (t=0.68s). Average Precision (AP) @[ IoU=0.50:0.95 | area= all | maxDets=100 ] = 0.900 Average Precision (AP) @[ IoU=0.50 | area= all | maxDets=100 ] = 0.984 Average Precision (AP) @[ IoU=0.75 | area= all | maxDets=100 ] = 0.984 Average Precision (AP) @[ IoU=0.50:0.95 | area= small | maxDets=100 ] = -1.000 Average Precision (AP) @[ IoU=0.50:0.95 | area=medium | maxDets=100 ] = 0.865 Average Precision (AP) @[ IoU=0.50:0.95 | area= large | maxDets=100 ] = 0.941 Average Recall (AR) @[ IoU=0.50:0.95 | area= all | maxDets= 1 ] = 0.773 Average Recall (AR) @[ IoU=0.50:0.95 | area= all | maxDets= 10 ] = 0.921 Average Recall (AR) @[ IoU=0.50:0.95 | area= all | maxDets=100 ] = 0.921 Average Recall (AR) @[ IoU=0.50:0.95 | area= small | maxDets=100 ] = -1.000 Average Recall (AR) @[ IoU=0.50:0.95 | area=medium | maxDets=100 ] = 0.892 Average Recall (AR) @[ IoU=0.50:0.95 | area= large | maxDets=100 ] = 0.955