[notebooks] added proper backend for 1D plot

notebooks/elliptic_oned.ipynb

@@ -6,21 +6,8 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "%matplotlib"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
-   "source": [
-    "from pymor.analyticalproblems.domaindescriptions import LineDomain\n",
-    "from pymor.analyticalproblems.elliptic import StationaryProblem\n",
-    "from pymor.discretizers.builtin import discretize_stationary_cg\n",
-    "from pymor.analyticalproblems.functions import ConstantFunction, ExpressionFunction, LincombFunction\n",
-    "from pymor.parameters.functionals import ProjectionParameterFunctional\n",
-    "#from ipywidgets import interact, widgets"
+    "from pymor.basic import *\n",
+    "set_defaults({'pymor.discretizers.builtin.gui.jupyter.get_visualizer.backend': 'not pythreejs'})"
    ]
   },
   {