Update deepspeed_lr_schedules.py (#314)

deepspeed/pt/deepspeed_lr_schedules.py

@@ -679,7 +679,7 @@ class WarmupLR(object):
         if self.last_batch_iteration < 0:
             logger.warning(
                 "Attempting to get learning rate from scheduler before it has started")
-            return 0.0
+            return [0.0]
         gamma = self._get_gamma()
         return [
             min_lr + (delta_lr * gamma) for min_lr,