feat: add isTemplate var to notebook template (#960)

# Description
Modify the notebook template to enable notebook testing. Change
PROJECT_ID and LOCATION cells to use environment variables if the user
doesn't provide a Project ID. Add a cell to load models in the template
to incorporate the isTemplate field.

---------

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

notebook_template.ipynb

@@ -302,12 +302,17 @@
       },
       "outputs": [],
       "source": [
-        "PROJECT_ID = \"[your-project-id]\"  # @param {type:\"string\"}\n",
-        "LOCATION = \"us-central1\"  # @param {type:\"string\"}\n",
-        "\n",
+        "# Use the environment variable if the user doesn't provide Project ID.\n",
+        "import os\n",
         "\n",
         "import vertexai\n",
         "\n",
+        "PROJECT_ID = \"[your-project-id]\"  # @param {type:\"string\", isTemplate: true}\n",
+        "if PROJECT_ID == \"[your-project-id]\":\n",
+        "    PROJECT_ID = str(os.environ.get(\"GOOGLE_CLOUD_PROJECT\"))\n",
+        "\n",
+        "LOCATION = os.environ.get(\"GOOGLE_CLOUD_REGION\", \"us-central1\")\n",
+        "\n",
         "vertexai.init(project=PROJECT_ID, location=LOCATION)"
       ]
     },
@@ -340,6 +345,27 @@
         "# TODO: Add all library imports here"
       ]
     },
+    {
+      "cell_type": "markdown",
+      "metadata": {
+        "id": "e43229f3ad4f"
+      },
+      "source": [
+        "### Load model"
+      ]
+    },
+    {
+      "cell_type": "code",
+      "execution_count": null,
+      "metadata": {
+        "id": "cf93d5f0ce00"
+      },
+      "outputs": [],
+      "source": [
+        "# TODO: Uncomment and add model name\n",
+        "# MODEL_ID = \"\"  # @param {type:\"string\", isTemplate: true}"
+      ]
+    },
     {
       "cell_type": "markdown",
       "metadata": {