Fix bug in gradient accumulation implementation

Author: johnowhitaker

unit2/01_finetuning_and_guidance.ipynb

@@ -690,7 +690,7 @@
     "        loss.backward(loss)\n",
     "\n",
     "        # Gradient accumulation:\n",
-    "        if (i + 1) % grad_accumulation_steps == 0:\n",
+    "        if (step + 1) % grad_accumulation_steps == 0:\n",
     "            optimizer.step()\n",
     "            optimizer.zero_grad()\n",
     "\n",