解决问题
INFO: pip is looking at multiple versions of keras-preprocessing to determine which version is compatible with other requirements. This could take a while.
INFO: This is taking longer than usual. You might need to provide the dependency resolver with stricter constraints to reduce runtime. If you want to abort this run, you can press Ctrl + C to do so. To improve how pip performs, tell us what happened here: https://pip.pypa.io/surveys/backtracking
INFO: pip is looking at multiple versions of h5py to determine which version is compatible with other requirements. This could take a while.
INFO: pip is looking at multiple versions of grpcio to determine which version is compatible with other requirements. This could take a while.
解决思路
信息：pip正在研究keras预处理的多个版本，以确定哪个版本与其他需求兼容。这可能需要一段时间。
信息：这比通常需要更长的时间。您可能需要为依赖项解析程序提供更严格的约束以减少运行时间。如果要中止此运行，可以按Ctrl+C来中止。要改进pip的执行方式，请在此处告诉我们发生了什么：https://pip.pypa.io/surveys/backtracking
信息：pip正在研究h5py的多个版本，以确定哪个版本与其他要求兼容。这可能需要一段时间。
信息：pip正在研究grpcio的多个版本，以确定哪个版本与其他需求兼容。这可能需要一段时间。
解决方法
参考文章：成功解决WARNING: Retrying (Retry(total=0, connect=None, read=None, redirect=None, status=None)) after co
