[Bug]: Figure manager is gone - AttributeError: 'NoneType' object has no attribute 'canvas'  #18

 File ~/work/conflowgen/conflowgen/conflowgen/analyses/inbound_and_outbound_vehicle_capacity_analysis_report.py:77, in InboundAndOutboundVehicleCapacityAnalysisReport.get_report_as_graph(self, **kwargs)
     71 df = pd.DataFrame({
     72     "inbound volume (in TEU)": inbound_capacities,
     73     "outbound volume (in TEU)": outbound_actual_capacities,
     74     "outbound maximum capacity": outbound_maximum_capacities
     75 })
     76 df.index = [str(i).replace("_", " ") for i in df.index]
---> 77 ax = df.plot.barh()
     78 ax.set_xlabel("Capacity (in TEU)")
     79 ax.set_title("Inbound and outbound vehicle capacity analysis")

File ~/.local/lib/python3.8/site-packages/pandas/plotting/_core.py:1217, in PlotAccessor.barh(self, x, y, **kwargs)
   1133 @Appender(
   1134     """
   1135     See Also
   (...)
   1206 @Appender(_bar_or_line_doc)
   1207 def barh(self, x=None, y=None, **kwargs):
   1208     """
   1209     Make a horizontal bar plot.
   1210 
   (...)
   1215     other axis represents a measured value.
   1216     """
-> 1217     return self(kind="barh", x=x, y=y, **kwargs)

File ~/.local/lib/python3.8/site-packages/pandas/plotting/_core.py:972, in PlotAccessor.__call__(self, *args, **kwargs)
    969             label_name = label_kw or data.columns
    970             data.columns = label_name
--> 972 return plot_backend.plot(data, kind=kind, **kwargs)

File ~/.local/lib/python3.8/site-packages/pandas/plotting/_matplotlib/__init__.py:71, in plot(data, kind, **kwargs)
     69         kwargs["ax"] = getattr(ax, "left_ax", ax)
     70 plot_obj = PLOT_CLASSES[kind](data, **kwargs)
---> 71 plot_obj.generate()
     72 plot_obj.draw()
     73 return plot_obj.result

File ~/.local/lib/python3.8/site-packages/pandas/plotting/_matplotlib/core.py:328, in MPLPlot.generate(self)
    326 self._args_adjust()
    327 self._compute_plot_data()
--> 328 self._setup_subplots()
    329 self._make_plot()
    330 self._add_table()

File ~/.local/lib/python3.8/site-packages/pandas/plotting/_matplotlib/core.py:386, in MPLPlot._setup_subplots(self)
    384 else:
    385     if self.ax is None:
--> 386         fig = self.plt.figure(figsize=self.figsize)
    387         axes = fig.add_subplot(111)
    388     else:

File ~/.local/lib/python3.8/site-packages/matplotlib/pyplot.py:810, in figure(num, figsize, dpi, facecolor, edgecolor, frameon, FigureClass, clear, **kwargs)
    798     _api.warn_external(
    799         f"More than {max_open_warning} figures have been opened. "
    800         f"Figures created through the pyplot interface "
   (...)
    803         f"warning, see the rcParam `figure.max_open_warning`).",
    804         RuntimeWarning)
    806 manager = new_figure_manager(
    807     num, figsize=figsize, dpi=dpi,
    808     facecolor=facecolor, edgecolor=edgecolor, frameon=frameon,
    809     FigureClass=FigureClass, **kwargs)
--> 810 fig = manager.canvas.figure
    811 if fig_label:
    812     fig.set_label(fig_label)

AttributeError: 'NoneType' object has no attribute 'canvas'
AttributeError: 'NoneType' object has no attribute 'canvas'