feat: Add explicit model selection in notebook

Author: salanki

nbs/demo_colab.ipynb

@@ -62,7 +62,9 @@
         "\n",
         "\n",
         "stability_api = client.StabilityInference(\n",
-        "    key=os.environ['STABILITY_KEY'], \n",
+        "    key=os.environ['STABILITY_KEY'],\n",
+        "    # Optional: Specify a specific model/checkpoint. Will use the default model as defined in the Python SDK release currently used if not specified. \n",
+        "    engine=\"stable-diffusion-v1-5\",\n",
         "    verbose=True,\n",
         ")"
       ]