add RADAM reference

utils/radam.py

@@ -3,6 +3,7 @@ import torch
 from torch.optim.optimizer import Optimizer
 
 
+# adapted from https://github.com/LiyuanLucasLiu/RAdam
 class RAdam(Optimizer):
 
     def __init__(self, params, lr=1e-3, betas=(0.9, 0.999), eps=1e-8, weight_decay=0):