Updates to tutorial and run post codacy changes

tutorials/tutorial12/tutorial.ipynb

@@ -60,14 +60,14 @@
     "if IN_COLAB:\n",
     "  !pip install \"pina-mathlab\"\n",
     "\n",
+    "import torch\n",
+    "\n",
     "#useful imports\n",
     "from pina.problem import SpatialProblem, TimeDependentProblem\n",
     "from pina.equation import Equation, FixedValue\n",
     "from pina.domain import CartesianDomain\n",
-    "import torch\n",
     "from pina.operator import grad, laplacian\n",
-    "from pina import Condition\n",
-    "\n"
+    "from pina import Condition"
    ]
   },
   {