Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/26390
`quantize_script`: top level API for graph mode quantization
Test Plan:
there are some known issues, we can enable test after all known issues are fixed.
Imported from OSS
Differential Revision: D17645132
fbshipit-source-id: 61f261d5607409d493b39a2f4e05ebd017279f6b
