added additional comment to toymedianThreshold example

Author: tclose

new-docs/source/tutorial/6-workflow.ipynb

@@ -482,12 +482,17 @@
     "    @python.define\n",
     "    def Median(mih: mrtrix3.ImageHeader) -> float:\n",
     "        \"\"\"A bespoke function that reads the separate data file in the MRTrix3 image\n",
-    "        header format (i.e. .mih) and calculates the median value.\"\"\"\n",
+    "        header format (i.e. .mih) and calculates the median value.\n",
+    "\n",
+    "        NB: We could use a MrStats task here, but this is just an example to show how\n",
+    "        to use a bespoke function in a workflow.\n",
+    "        \"\"\"\n",
     "        dtype = MRTRIX2NUMPY_DTYPES[mih.metadata[\"datatype\"].strip()]\n",
     "        data = np.frombuffer(Path.read_bytes(mih.data_file), dtype=dtype)\n",
     "        return np.median(data)\n",
     "\n",
     "    median = workflow.add(Median(mih=input_conversion.out_file))\n",
+    "\n",
     "    threshold = workflow.add(\n",
     "        MrThreshold(in_file=in_image, out_file=\"binary.mif\", abs=median.out),\n",
     "        environment=Docker(\"mrtrix3/mrtrix3\", tag=\"latest\"),\n",