Update usage example

Author: constantinpape

example/bioimageio-core-usage.ipynb

@@ -313,6 +313,32 @@
     "Here, we will use this functionality to create two models, one that adds thresholding of the outputs as post-processing and another that also adds weights in torchscript format."
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "a210a1f7",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# get the python file defining the architecture\n",
+    "def get_architecture_source(rdf):\n",
+    "    # here, we need the raw resource, which contains the information from the resource description\n",
+    "    # before evaluation, e.g. the file and name of the python file with the model architecture\n",
+    "    raw_resource = bioimageio.core.load_raw_resource_description(rdf)\n",
+    "    # the source information\n",
+    "    model_source = raw_resource.source\n",
+    "    # download the source file if necessary\n",
+    "    source_file = bioimageio.core.resource_io.utils.resolve_uri(\n",
+    "        model_source.source_file\n",
+    "    )\n",
+    "    # if the source file path does not exist, try combining it with the root path of the model\n",
+    "    if not os.path.exists(source_file):\n",
+    "        source_file = os.path.join(raw_resource.root_path, source_file)\n",
+    "    assert os.path.exists(source_file), source_file\n",
+    "    class_name = model_source.callable_name\n",
+    "    return f\"{source_file}:{class_name}\""
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": null,
@@ -340,10 +366,9 @@
     "]\n",
     "postprocessing = [{\"binarize\": {\"threshold\": threshold}}]\n",
     "\n",
-    "# copy the file containing the source code for the model architecture to the model output folder\n",
-    "model_path = os.path.join(model_resource.root_path, \"unet.py\")\n",
-    "assert os.path.exists(model_path), model_path\n",
-    "model_source = f\"{model_path}:UNet2d\"\n",
+    "# get the model architecture\n",
+    "# note that this is only necessary for pytorch state dict models\n",
+    "model_source = get_architecture_source(rdf_doi)\n",
     "\n",
     "# we use the `parent` field to indicate that the new model is created based on\n",
     "# the nucleus segmentation model we have obtained from bioimage.io\n",