diff --git a/docs/notebooks/notebook_1_sarc_connection_and_users_list.ipynb b/docs/notebooks/notebook_1_sarc_connection_and_users_list.ipynb
index 4f19178f..e2d13b09 100644
--- a/docs/notebooks/notebook_1_sarc_connection_and_users_list.ipynb
+++ b/docs/notebooks/notebook_1_sarc_connection_and_users_list.ipynb
@@ -112,15 +112,15 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "supervisors = []\n",
-    "co_supervisors = []\n",
+    "supervisors = set()\n",
+    "co_supervisors = set()\n",
     "for user in users:\n",
     "    supervisor = user.mila_ldap.get(\"supervisor\")\n",
     "    co_supervisor = user.mila_ldap.get(\"co_supervisor\")\n",
     "    if supervisor:\n",
-    "        supervisors.append(supervisor)\n",
+    "        supervisors.add(supervisor)\n",
     "    if co_supervisor:\n",
-    "        co_supervisors.append(co_supervisor)\n",
+    "        co_supervisors.add(co_supervisor)\n",
     "print(f\"Number of supervisors: {len(supervisors)}\")\n",
     "print(f\"Number of co-supervisors: {len(co_supervisors)}\")"
    ]