ggplot(df) + \
    geom_tile(aes(x = 'x', y = 'y',  width = 1, height = 1, fill = 'value')) + \
    theme_void()

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
~/.local/lib/python3.6/site-packages/IPython/core/formatters.py in __call__(self, obj)
    700                 type_pprinters=self.type_printers,
    701                 deferred_pprinters=self.deferred_printers)
--> 702             printer.pretty(obj)
    703             printer.flush()
    704             return stream.getvalue()
~/.local/lib/python3.6/site-packages/IPython/lib/pretty.py in pretty(self, obj)
    397                         if cls is not object \
    398                                 and callable(cls.__dict__.get('__repr__')):
--> 399                             return _repr_pprint(obj, self, cycle)
    400
    401             return _default_pprint(obj, self, cycle)
~/.local/lib/python3.6/site-packages/IPython/lib/pretty.py in _repr_pprint(obj, p, cycle)
    687     """A pprint that just redirects to the normal repr function."""
    688     # Find newlines and replace them with p.break_()
--> 689     output = repr(obj)
    690     for idx,output_line in enumerate(output.splitlines()):
    691         if idx:
~/.local/lib/python3.6/site-packages/plotnine/ggplot.py in __repr__(self)
     86         # in the jupyter notebook.
     87         if not self.figure:
---> 88             self.draw()
     89         plt.show()
     90         return '<ggplot: (%d)>' % self.__hash__()
~/.local/lib/python3.6/site-packages/plotnine/ggplot.py in draw(self, return_ggplot)
    179         # new frames knowing that they are separate from the original.
    180         with pd.option_context('mode.chained_assignment', None):
--> 181             return self._draw(return_ggplot)
    182
    183     def _draw(self, return_ggplot=False):
~/.local/lib/python3.6/site-packages/plotnine/ggplot.py in _draw(self, return_ggplot)
    210             if self.figure is not None:
    211                 plt.close(self.figure)
--> 212             raise err
    213
    214         if return_ggplot:
~/.local/lib/python3.6/site-packages/plotnine/ggplot.py in _draw(self, return_ggplot)
    202                 self._draw_labels()
    203                 self._draw_breaks_and_labels()
--> 204                 self._draw_legend()
    205                 self._draw_title()
    206                 self._draw_watermarks()
~/.local/lib/python3.6/site-packages/plotnine/ggplot.py in _draw_legend(self)
    421         Draw legend onto the figure
    422         """
--> 423         legend_box = self.guides.build(self)
    424         if not legend_box:
    425             return
~/.local/lib/python3.6/site-packages/plotnine/guides/guides.py in build(self, plot)
    142             return
    143
--> 144         gboxes = self.draw(gdefs, plot.theme)
    145         bigbox = self.assemble(gboxes, gdefs, plot.theme)
    146         return bigbox
~/.local/lib/python3.6/site-packages/plotnine/guides/guides.py in draw(self, gdefs, theme)
    284             g.theme = theme
    285             g._set_defaults()
--> 286         return [g.draw() for g in gdefs]
    287
    288     def assemble(self, gboxes, gdefs, theme):
~/.local/lib/python3.6/site-packages/plotnine/guides/guides.py in <listcomp>(.0)
    284             g.theme = theme
    285             g._set_defaults()
--> 286         return [g.draw() for g in gdefs]
    287
    288     def assemble(self, gboxes, gdefs, theme):
~/.local/lib/python3.6/site-packages/plotnine/guides/guide_colorbar.py in draw(self)
    152         # 1.45 makes the default colourbar wider than the
    153         # legend entry boxes.
--> 154         width = (self.barwidth or _d('legend_key_width')) * 1.45
    155         height = (self.barheight or _d('legend_key_height')) * 1.45
    156         height *= 5
TypeError: unsupported operand type(s) for *: 'NoneType' and 'float'