Show off `%%julia` magic in notebook example

examples/pysr_demo.ipynb

@@ -796,7 +796,24 @@
    },
    "outputs": [],
    "source": [
-    "jl.seval(\"import Primes\")"
+    "jl.seval(\"using Primes: prime\")"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Note that PySR should automatically load the `juliacall.ipython` extension for you,\n",
+    "which means that you can also execute Julia code in the notebook using the `%%julia` magic:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "%julia using Primes: prime"
    ]
   },
   {
@@ -821,7 +838,7 @@
     "    \"\"\"\n",
     "function p(i::T) where T\n",
     "    if 0.5 < i < 1000\n",
-    "        return T(Primes.prime(round(Int, i)))\n",
+    "        return T(prime(round(Int, i)))\n",
     "    else\n",
     "        return T(NaN)\n",
     "    end\n",
@@ -830,6 +847,29 @@
     ")"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Or, equivalently:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "%%julia\n",
+    "function p(i::T) where T\n",
+    "    if 0.5 < i < 1000\n",
+    "        return T(prime(round(Int, i)))\n",
+    "    else\n",
+    "        return T(NaN)\n",
+    "    end\n",
+    "end"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {