can't install insightface

when I use the way of "pip install -r requirements" to install "insightface", I find setup.py must contain numpy and Cython package first,but my machine didn't own any package at first, so even if I put the numpy and Cython at the top of requirements.txt, the setup.py still can't find out and check numpy and Cython package correctly, It will throw error like "no moudle 'numpy' found out". In some specific scenario, I must install packages by requirements.txt rather than using pip numpy first. So how can I address this problem?

Reproduce the failure in a clean environment with `pip install -r requirements.txt`, then inspect `setup.py` and `requirements.txt` to understand the dependency-order problem. Done means the project installs successfully from the requirements file without preinstalling numpy or Cython.

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