diff --git a/tracetools_analysis/analysis/callback_duration.ipynb b/tracetools_analysis/analysis/callback_duration.ipynb
index 142286a..f624140 100644
--- a/tracetools_analysis/analysis/callback_duration.ipynb
+++ b/tracetools_analysis/analysis/callback_duration.ipynb
@@ -11,7 +11,7 @@
     "# Get trace data using the provided launch file:\n",
     "#    $ ros2 launch tracetools_analysis pingpong.launch.py\n",
     "#    (wait a few seconds, then kill with Ctrl+C)\n",
-    "#\n",
+    "# AND\n",
     "# Convert trace data:\n",
     "#    $ ros2 run tracetools_analysis convert ~/.ros/tracing/pingpong/ust\n",
     "#\n",
@@ -104,27 +104,46 @@
     "    duration_df = data_util.get_callback_durations(obj)\n",
     "    starttime = duration_df.loc[:, 'timestamp'].iloc[0].strftime('%Y-%m-%d %H:%M')\n",
     "    source = ColumnDataSource(duration_df)\n",
-    "    duration = figure(title=owner_info,\n",
-    "                      x_axis_label=f'start ({starttime})',\n",
-    "                      y_axis_label='duration (ms)',\n",
-    "                      plot_width=psize, plot_height=psize)\n",
+    "    duration = figure(\n",
+    "        title=owner_info,\n",
+    "        x_axis_label=f'start ({starttime})',\n",
+    "        y_axis_label='duration (ms)',\n",
+    "        plot_width=psize, plot_height=psize,\n",
+    "    )\n",
     "    duration.title.align = 'center'\n",
-    "    duration.line(x='timestamp', y='duration', legend=str(symbol), line_width=2, source=source, line_color=colours[colour_i])\n",
+    "    duration.line(\n",
+    "        x='timestamp',\n",
+    "        y='duration',\n",
+    "        legend=str(symbol),\n",
+    "        line_width=2,\n",
+    "        source=source,\n",
+    "        line_color=colours[colour_i],\n",
+    "    )\n",
     "    duration.legend.label_text_font_size = '11px'\n",
     "    duration.xaxis[0].formatter = DatetimeTickFormatter(seconds=['%Ss'])\n",
     "\n",
     "    # Histogram\n",
     "    dur_hist, edges = np.histogram(duration_df['duration'])\n",
-    "    duration_hist = pd.DataFrame({'duration': dur_hist, \n",
-    "                                     'left': edges[:-1], \n",
-    "                                     'right': edges[1:]})\n",
-    "    hist = figure(title='Duration histogram',\n",
-    "                  x_axis_label='duration (ms)',\n",
-    "                  y_axis_label='frequency',\n",
-    "                  plot_width=psize, plot_height=psize)\n",
+    "    duration_hist = pd.DataFrame({\n",
+    "        'duration': dur_hist, \n",
+    "        'left': edges[:-1], \n",
+    "        'right': edges[1:],\n",
+    "    })\n",
+    "    hist = figure(\n",
+    "        title='Duration histogram',\n",
+    "        x_axis_label='duration (ms)',\n",
+    "        y_axis_label='frequency',\n",
+    "        plot_width=psize, plot_height=psize,\n",
+    "    )\n",
     "    hist.title.align = 'center'\n",
-    "    hist.quad(bottom=0, top=duration_hist['duration'], \n",
-    "              left=duration_hist['left'], right=duration_hist['right'], fill_color=colours[colour_i], line_color=colours[colour_i])\n",
+    "    hist.quad(\n",
+    "        bottom=0,\n",
+    "        top=duration_hist['duration'], \n",
+    "        left=duration_hist['left'],\n",
+    "        right=duration_hist['right'],\n",
+    "        fill_color=colours[colour_i],\n",
+    "        line_color=colours[colour_i],\n",
+    "    )\n",
     "\n",
     "    colour_i += 1\n",
     "    show(row(duration, hist))"
@@ -145,17 +164,26 @@
     "        earliest_date = thedate\n",
     "\n",
     "starttime = earliest_date.strftime('%Y-%m-%d %H:%M')\n",
-    "duration = figure(title='Callback durations',\n",
-    "                  x_axis_label=f'start ({starttime})',\n",
-    "                  y_axis_label='duration (ms)',\n",
-    "                  plot_width=psize, plot_height=psize)\n",
+    "duration = figure(\n",
+    "    title='Callback durations',\n",
+    "    x_axis_label=f'start ({starttime})',\n",
+    "    y_axis_label='duration (ms)',\n",
+    "    plot_width=psize, plot_height=psize,\n",
+    ")\n",
     "\n",
     "colour_i = 0\n",
     "for obj, symbol in callback_symbols.items():\n",
     "    duration_df = data_util.get_callback_durations(obj)\n",
     "    source = ColumnDataSource(duration_df)\n",
     "    duration.title.align = 'center'\n",
-    "    duration.line(x='timestamp', y='duration', legend=str(symbol), line_width=2, source=source, line_color=colours[colour_i])\n",
+    "    duration.line(\n",
+    "        x='timestamp',\n",
+    "        y='duration',\n",
+    "        legend=str(symbol),\n",
+    "        line_width=2,\n",
+    "        source=source,\n",
+    "        line_color=colours[colour_i],\n",
+    "    )\n",
     "    colour_i += 1\n",
     "    duration.legend.label_text_font_size = '11px'\n",
     "    duration.xaxis[0].formatter = DatetimeTickFormatter(seconds=['%Ss'])\n",