Automatize Tutorials html, py files creation (#496)

* workflow to export tutorials

---------

tutorials/tutorial3/tutorial.ipynb

@@ -23,13 +23,14 @@
    "source": [
     "## routine needed to run the notebook on Google Colab\n",
     "try:\n",
-    "  import google.colab\n",
-    "  IN_COLAB = True\n",
+    "    import google.colab\n",
+    "\n",
+    "    IN_COLAB = True\n",
     "except:\n",
-    "  IN_COLAB = False\n",
+    "    IN_COLAB = False\n",
     "if IN_COLAB:\n",
-    "  !pip install \"pina-mathlab\"\n",
-    "  \n",
+    "    !pip install \"pina-mathlab\"\n",
+    "\n",
     "import torch\n",
     "import matplotlib.pyplot as plt\n",
     "import warnings\n",
@@ -42,7 +43,7 @@
     "from pina.equation import Equation, FixedValue\n",
     "from pina.callback import MetricTracker\n",
     "\n",
-    "warnings.filterwarnings('ignore')"
+    "warnings.filterwarnings(\"ignore\")"
    ]
   },
   {
@@ -261,7 +262,7 @@
     "    train_size=1.0,\n",
     "    val_size=0.0,\n",
     "    test_size=0.0,\n",
-    "    callbacks=[MetricTracker(['train_loss', 'initial_loss','D_loss'])],\n",
+    "    callbacks=[MetricTracker([\"train_loss\", \"initial_loss\", \"D_loss\"])],\n",
     ")\n",
     "trainer.train()"
    ]
@@ -343,10 +344,10 @@
     "        \"True solution\": problem.solution(points),\n",
     "        \"Absolute Difference\": torch.abs(\n",
     "            solver(points) - problem.solution(points)\n",
-    "        )\n",
+    "        ),\n",
     "    }\n",
     "    # plot the solution\n",
-    "    plt.suptitle(f'Solution for time {time.item()}')\n",
+    "    plt.suptitle(f\"Solution for time {time.item()}\")\n",
     "    for idx, (title, field) in enumerate(data.items()):\n",
     "        plt.subplot(1, 3, idx + 1)\n",
     "        plt.title(title)\n",