萃取原理
========================================================

.. raw:: html


   <video width="100%" height="100%" controls>
   <source src="https://outin-0fed40cae50711eaa61200163e1c94a4.oss-cn-shanghai.aliyuncs.com/sv/4ca017c8-17986d4450e/4ca017c8-17986d4450e.mp4" type="video/mp4" />
   </video>