fix undefined variables in fine tune example (#660)

`create_user_message` and `test_df` are not defined.

examples/How_to_finetune_chat_models.ipynb

@@ -253,11 +253,14 @@
     "\n",
     "system_message = \"You are a helpful recipe assistant. You are to extract the generic ingredients from each of the recipes provided.\"\n",
     "\n",
+    "def create_user_message(row):\n",
+    "    return f\"\"\"Title: {row['title']}\\n\\nIngredients: {row['ingredients']}\\n\\nGeneric ingredients: \"\"\"\n",
+    "\n",
     "def prepare_example_conversation(row):\n",
     "    messages = []\n",
     "    messages.append({\"role\": \"system\", \"content\": system_message})\n",
     "\n",
-    "    user_message = f\"\"\"Title: {row['title']}\\n\\nIngredients: {row['ingredients']}\\n\\nGeneric ingredients: \"\"\"\n",
+    "    user_message = create_user_message(row)\n",
     "    messages.append({\"role\": \"user\", \"content\": user_message})\n",
     "\n",
     "    messages.append({\"role\": \"assistant\", \"content\": row[\"NER\"]})\n",
@@ -642,6 +645,7 @@
     }
    ],
    "source": [
+    "test_df = recipe_df.loc[201:300]\n",
     "test_row = test_df.iloc[0]\n",
     "test_messages = []\n",
     "test_messages.append({\"role\": \"system\", \"content\": system_message})\n",