Fix Altair PNG rendering and seaborn kdeplot API in notebook

Restore alt.renderers.enable('png') that was dropped during the 2025
modernization attempt, and replace removed kdeplot shade= with fill=.

Author: tdhopper

Examples.ipynb

@@ -5,52 +5,7 @@
    "execution_count": null,
    "metadata": {},
    "outputs": [],
-   "source": [
-    "%matplotlib inline\n",
-    "\n",
-    "import readline\n",
-    "import altair as alt\n",
-    "import pandas as pd\n",
-    "import seaborn as sns\n",
-    "from matplotlib import pyplot\n",
-    "from plotnine import *\n",
-    "import numpy as np\n",
-    "\n",
-    "from plotly import figure_factory\n",
-    "from plotly import graph_objects\n",
-    "import plotly.express as px\n",
-    "from IPython.core.magic import Magics, magics_class, cell_magic\n",
-    "\n",
-    "from IPython.display import Image\n",
-    "\n",
-    "from pylab import rcParams\n",
-    "\n",
-    "size = 20\n",
-    "params = {\n",
-    "    \"legend.fontsize\": size,\n",
-    "    \"figure.figsize\": (15, 5),\n",
-    "    \"axes.labelsize\": size,\n",
-    "    \"axes.titlesize\": size,\n",
-    "    \"xtick.labelsize\": size,\n",
-    "    \"ytick.labelsize\": size,\n",
-    "    \"axes.titlesize\": 1.5 * size,\n",
-    "    \"figure.figsize\": (12, 12),\n",
-    "}\n",
-    "rcParams.update(params)\n",
-    "theme_update(\n",
-    "    figure_size=(9, 9),\n",
-    "    title=element_text(size=size),\n",
-    "    text=element_text(size=0.6 * size),\n",
-    ")  # for plotnine\n",
-    "\n",
-    "\n",
-    "import plotly.io as pio\n",
-    "pio.renderers.default = \"png\"\n",
-    "pio.renderers[\"png\"].width = 750\n",
-    "pio.renderers[\"png\"].height = 750\n",
-    "\n",
-    "# For now, use default (will show as objects)"
-   ]
+   "source": "%matplotlib inline\n\nimport readline\nimport altair as alt\nimport pandas as pd\nimport seaborn as sns\nfrom matplotlib import pyplot\nfrom plotnine import *\nimport numpy as np\n\nfrom plotly import figure_factory\nfrom plotly import graph_objects\nimport plotly.express as px\nfrom IPython.core.magic import Magics, magics_class, cell_magic\n\nfrom IPython.display import Image\n\nfrom pylab import rcParams\n\nsize = 20\nparams = {\n    \"legend.fontsize\": size,\n    \"figure.figsize\": (15, 5),\n    \"axes.labelsize\": size,\n    \"axes.titlesize\": size,\n    \"xtick.labelsize\": size,\n    \"ytick.labelsize\": size,\n    \"axes.titlesize\": 1.5 * size,\n    \"figure.figsize\": (12, 12),\n}\nrcParams.update(params)\ntheme_update(\n    figure_size=(9, 9),\n    title=element_text(size=size),\n    text=element_text(size=0.6 * size),\n)  # for plotnine\n\n\nimport plotly.io as pio\npio.renderers.default = \"png\"\npio.renderers[\"png\"].width = 750\npio.renderers[\"png\"].height = 750\n\n# Render Altair charts as PNG via vl-convert\nalt.renderers.enable(\"png\", scale_factor=2.0)"
   },
   {
    "cell_type": "code",
@@ -1554,16 +1509,7 @@
     ]
    },
    "outputs": [],
-   "source": [
-    "(sns\n",
-    "  .FacetGrid(diamonds, \n",
-    "             hue=\"cut\", \n",
-    "             height=10, \n",
-    "             xlim=(55, 70))\n",
-    "  .map(sns.kdeplot, 'depth', shade=True)\n",
-    " .add_legend()\n",
-    ");"
-   ]
+   "source": "(sns\n  .FacetGrid(diamonds, \n             hue=\"cut\", \n             height=10, \n             xlim=(55, 70))\n  .map(sns.kdeplot, 'depth', fill=True)\n .add_legend()\n);"
   },
   {
    "cell_type": "code",