AttributeError: module 'cv2.dnn' has no attribute 'DictValue'
这个错误，以及下面这个错误：
AttributeError: partially initialized module 'cv2' has no attribute 'gapi_wip_gst_GStreamerPipeline' (most likely due to a circular import)
如果你同时安装了 opencv-python 和 opencv-python-headless ，则有可能是冲突导致，可尝试卸载掉 opencv-python-headless