how to add new model of face recognize

**Is your feature request related to a problem? Please describe.**
the accuracy of face recognize is not very well.

**Describe the solution you'd like**
I want to add the model of face recognize

however , I don't know the function of the number param , could you provide the guide for add model
```
ml_models = (
('arcface_mobilefacenet', '17TpxpyHuUc1ZTm3RIbfvhnBcZqhyKszV', (1.26538905, 5.552089201), 200),
('arcface_r100_v1', '11xFaEHIQLNze3-2RUV1cQfT-q6PKKfYp', (1.23132175, 6.602259425), 400),
('arcface_resnet34', '1ECp5XrLgfEAnwyTYFEhJgIsOAw6KaHa7', (1.2462842, 5.981636853), 400),
('arcface_resnet50', '1a9nib4I9OIVORwsqLB0gz0WuLC32E8gf', (1.2375747, 5.973354538), 400),
('arcface-r50-msfdrop75', '1gNuvRNHCNgvFtz7SjhW82v2-znlAYaRO', (1.2350148, 7.071431642), 400),
('arcface-r100-msfdrop75', '1lAnFcBXoMKqE-SkZKTmi6MsYAmzG0tFw', (1.224676, 6.322647217), 400),
# CASIA-WebFace-Masked, 0.9840 LFW, 0.9667 LFW-Masked (orig mobilefacenet has 0.9482 on LFW-Masked)
('arcface_mobilefacenet_casia_masked', '1ltcJChTdP1yQWF9e1ESpTNYAVwxLSNLP', (1.22507105, 7.321198934), 200),
)
```