Adds bounds axes.  Shows the bounds of the most recent input
        mesh unless mesh is specified.

        Parameters
        ----------
        mesh : vtkPolydata or unstructured grid, optional
            Input mesh to draw bounds axes around

        bounds : list or tuple, optional
            Bounds to override mesh bounds.
            [xmin, xmax, ymin, ymax, zmin, zmax]

        show_xaxis : bool, optional
            Makes x axis visible.  Default True.

        show_yaxis : bool, optional
            Makes y axis visible.  Default True.

        show_zaxis : bool, optional
            Makes z axis visible.  Default True.

        show_xlabels : bool, optional
            Shows x labels.  Default True.

        show_ylabels : bool, optional
            Shows y labels.  Default True.

        show_zlabels : bool, optional
            Shows z labels.  Default True.

        italic : bool, optional
            Italicises axis labels and numbers.  Default False.

        bold : bool, optional
            Bolds axis labels and numbers.  Default True.

        shadow : bool, optional
            Adds a black shadow to the text.  Default False.

        font_size : float, optional
            Sets the size of the label font.  Defaults to 16.

        font_family : string, optional
            Font family.  Must be either courier, times, or arial.

        color : string or 3 item list, optional
            Color of all labels and axis titles.  Default white.
            Either a string, rgb list, or hex color string.  For example:

                color='white'
                color='w'
                color=[1, 1, 1]
                color='#FFFFFF'

        xlabel : string, optional
            Title of the x axis.  Default "X Axis"

        ylabel : string, optional
            Title of the y axis.  Default "Y Axis"

        zlabel : string, optional
            Title of the z axis.  Default "Z Axis"

        use_2d : bool, optional
            A bug with vtk 6.3 in Windows seems to cause this function
            to crash this can be enabled for smoother plotting for
            other enviornments.

        grid : bool or str, optional
            Add grid lines to the backface (``True``, ``'back'``, or
            ``'backface'``) or to the frontface (``'front'``,
            ``'frontface'``) of the axes actor.

        location : str, optional
            Set how the axes are drawn: either static (``'all'``),
            closest triad (``front``), furthest triad (``'back'``),
            static closest to the origin (``'origin'``), or outer
            edges (``'outer'``) in relation to the camera
            position. Options include: ``'all', 'front', 'back',
            'origin', 'outer'``

        ticks : str, optional
            Set how the ticks are drawn on the axes grid. Options include:
            ``'inside', 'outside', 'both'``

        all_edges : bool, optional
            Adds an unlabeled and unticked box at the boundaries of
            plot. Useful for when wanting to plot outer grids while
            still retaining all edges of the boundary.

        corner_factor : float, optional
            If ``all_edges````, this is the factor along each axis to
            draw the default box. Dafuault is 0.5 to show the full box.

        loc : int, tuple, or list
            Index of the renderer to add the actor to.  For example,
            ``loc=2`` or ``loc=(1, 1)``.  If None, selects the last
            active Renderer.

        padding : float, optional
            An optional percent padding along each axial direction to cushion
            the datasets in the scene from the axes annotations. Defaults to
            have no padding

        Returns
        -------
        cube_axes_actor : vtk.vtkCubeAxesActor
            Bounds actor

        Examples
        --------
        >>> import vtki
        >>> from vtki import examples
        >>> mesh = vtki.Sphere()
        >>> plotter = vtki.Plotter()
        >>> _ = plotter.add_mesh(mesh)
        >>> _ = plotter.show_bounds(grid='front', location='outer', all_edges=True)
        >>> plotter.show() # doctest:+SKIP

def show_bounds(self, mesh=None, bounds=None, show_xaxis=True,
                    show_yaxis=True, show_zaxis=True, show_xlabels=True,
                    show_ylabels=True, show_zlabels=True, italic=False,
                    bold=True, shadow=False, font_size=None,
                    font_family=None, color=None,
                    xlabel='X Axis', ylabel='Y Axis', zlabel='Z Axis',
                    use_2d=False, grid=None, location='closest', ticks=None,
                    all_edges=False, corner_factor=0.5, loc=None, fmt=None,
                    minor_ticks=False, padding=0.0):
        """
        Adds bounds axes.  Shows the bounds of the most recent input
        mesh unless mesh is specified.

        Parameters
        ----------
        mesh : vtkPolydata or unstructured grid, optional
            Input mesh to draw bounds axes around

        bounds : list or tuple, optional
            Bounds to override mesh bounds.
            [xmin, xmax, ymin, ymax, zmin, zmax]

        show_xaxis : bool, optional
            Makes x axis visible.  Default True.

        show_yaxis : bool, optional
            Makes y axis visible.  Default True.

        show_zaxis : bool, optional
            Makes z axis visible.  Default True.

        show_xlabels : bool, optional
            Shows x labels.  Default True.

        show_ylabels : bool, optional
            Shows y labels.  Default True.

        show_zlabels : bool, optional
            Shows z labels.  Default True.

        italic : bool, optional
            Italicises axis labels and numbers.  Default False.

        bold : bool, optional
            Bolds axis labels and numbers.  Default True.

        shadow : bool, optional
            Adds a black shadow to the text.  Default False.

        font_size : float, optional
            Sets the size of the label font.  Defaults to 16.

        font_family : string, optional
            Font family.  Must be either courier, times, or arial.

        color : string or 3 item list, optional
            Color of all labels and axis titles.  Default white.
            Either a string, rgb list, or hex color string.  For example:

                color='white'
                color='w'
                color=[1, 1, 1]
                color='#FFFFFF'

        xlabel : string, optional
            Title of the x axis.  Default "X Axis"

        ylabel : string, optional
            Title of the y axis.  Default "Y Axis"

        zlabel : string, optional
            Title of the z axis.  Default "Z Axis"

        use_2d : bool, optional
            A bug with vtk 6.3 in Windows seems to cause this function
            to crash this can be enabled for smoother plotting for
            other enviornments.

        grid : bool or str, optional
            Add grid lines to the backface (``True``, ``'back'``, or
            ``'backface'``) or to the frontface (``'front'``,
            ``'frontface'``) of the axes actor.

        location : str, optional
            Set how the axes are drawn: either static (``'all'``),
            closest triad (``front``), furthest triad (``'back'``),
            static closest to the origin (``'origin'``), or outer
            edges (``'outer'``) in relation to the camera
            position. Options include: ``'all', 'front', 'back',
            'origin', 'outer'``

        ticks : str, optional
            Set how the ticks are drawn on the axes grid. Options include:
            ``'inside', 'outside', 'both'``

        all_edges : bool, optional
            Adds an unlabeled and unticked box at the boundaries of
            plot. Useful for when wanting to plot outer grids while
            still retaining all edges of the boundary.

        corner_factor : float, optional
            If ``all_edges````, this is the factor along each axis to
            draw the default box. Dafuault is 0.5 to show the full box.

        loc : int, tuple, or list
            Index of the renderer to add the actor to.  For example,
            ``loc=2`` or ``loc=(1, 1)``.  If None, selects the last
            active Renderer.

        padding : float, optional
            An optional percent padding along each axial direction to cushion
            the datasets in the scene from the axes annotations. Defaults to
            have no padding

        Returns
        -------
        cube_axes_actor : vtk.vtkCubeAxesActor
            Bounds actor

        Examples
        --------
        >>> import vtki
        >>> from vtki import examples
        >>> mesh = vtki.Sphere()
        >>> plotter = vtki.Plotter()
        >>> _ = plotter.add_mesh(mesh)
        >>> _ = plotter.show_bounds(grid='front', location='outer', all_edges=True)
        >>> plotter.show() # doctest:+SKIP
        """
        self.remove_bounds_axes()

        if font_family is None:
            font_family = rcParams['font']['family']
        if font_size is None:
            font_size = rcParams['font']['size']
        if color is None:
            color = rcParams['font']['color']
        if fmt is None:
            fmt = rcParams['font']['fmt']

        color = parse_color(color)

        # Use the bounds of all data in the rendering window
        if not mesh and not bounds:
            bounds = self.bounds

        # create actor
        cube_axes_actor = vtk.vtkCubeAxesActor()
        if use_2d or not np.allclose(self.scale, [1.0, 1.0, 1.0]):
            cube_axes_actor.SetUse2DMode(True)
        else:
            cube_axes_actor.SetUse2DMode(False)

        if grid:
            if isinstance(grid, str) and grid.lower() in ('front', 'frontface'):
                cube_axes_actor.SetGridLineLocation(cube_axes_actor.VTK_GRID_LINES_CLOSEST)
            if isinstance(grid, str) and grid.lower() in ('both', 'all'):
                cube_axes_actor.SetGridLineLocation(cube_axes_actor.VTK_GRID_LINES_ALL)
            else:
                cube_axes_actor.SetGridLineLocation(cube_axes_actor.VTK_GRID_LINES_FURTHEST)
            cube_axes_actor.DrawXGridlinesOn()
            cube_axes_actor.DrawYGridlinesOn()
            cube_axes_actor.DrawZGridlinesOn()
            # Set the colors
            cube_axes_actor.GetXAxesGridlinesProperty().SetColor(color)
            cube_axes_actor.GetYAxesGridlinesProperty().SetColor(color)
            cube_axes_actor.GetZAxesGridlinesProperty().SetColor(color)

        if isinstance(ticks, str):
            ticks = ticks.lower()
            if ticks in ('inside'):
                cube_axes_actor.SetTickLocationToInside()
            elif ticks in ('outside'):
                cube_axes_actor.SetTickLocationToOutside()
            elif ticks in ('both'):
                cube_axes_actor.SetTickLocationToBoth()
            else:
                raise ValueError('Value of ticks ({}) not understood.'.format(ticks))

        if isinstance(location, str):
            location = location.lower()
            if location in ('all'):
                cube_axes_actor.SetFlyModeToStaticEdges()
            elif location in ('origin'):
                cube_axes_actor.SetFlyModeToStaticTriad()
            elif location in ('outer'):
                cube_axes_actor.SetFlyModeToOuterEdges()
            elif location in ('default', 'closest', 'front'):
                cube_axes_actor.SetFlyModeToClosestTriad()
            elif location in ('furthest', 'back'):
                cube_axes_actor.SetFlyModeToFurthestTriad()
            else:
                raise ValueError('Value of location ({}) not understood.'.format(location))

        # set bounds
        if not bounds:
            bounds = np.array(mesh.GetBounds())
        if isinstance(padding, (int, float)) and 0.0 <= padding < 1.0:
            if not np.any(np.abs(bounds) == np.inf):
                cushion = np.array([np.abs(bounds[1] - bounds[0]),
                                    np.abs(bounds[3] - bounds[2]),
                                    np.abs(bounds[5] - bounds[4])]) * padding
                bounds[::2] -= cushion
                bounds[1::2] += cushion
        else:
            raise ValueError('padding ({}) not understood. Must be float between 0 and 1'.format(padding))
        cube_axes_actor.SetBounds(bounds)

        # show or hide axes
        cube_axes_actor.SetXAxisVisibility(show_xaxis)
        cube_axes_actor.SetYAxisVisibility(show_yaxis)
        cube_axes_actor.SetZAxisVisibility(show_zaxis)

        # disable minor ticks
        if not minor_ticks:
            cube_axes_actor.XAxisMinorTickVisibilityOff()
            cube_axes_actor.YAxisMinorTickVisibilityOff()
            cube_axes_actor.ZAxisMinorTickVisibilityOff()

        cube_axes_actor.SetCamera(self.camera)

        # set color
        cube_axes_actor.GetXAxesLinesProperty().SetColor(color)
        cube_axes_actor.GetYAxesLinesProperty().SetColor(color)
        cube_axes_actor.GetZAxesLinesProperty().SetColor(color)

        # empty arr
        empty_str = vtk.vtkStringArray()
        empty_str.InsertNextValue('')

        # show lines
        if show_xaxis:
            cube_axes_actor.SetXTitle(xlabel)
        else:
            cube_axes_actor.SetXTitle('')
            cube_axes_actor.SetAxisLabels(0, empty_str)

        if show_yaxis:
            cube_axes_actor.SetYTitle(ylabel)
        else:
            cube_axes_actor.SetYTitle('')
            cube_axes_actor.SetAxisLabels(1, empty_str)

        if show_zaxis:
            cube_axes_actor.SetZTitle(zlabel)
        else:
            cube_axes_actor.SetZTitle('')
            cube_axes_actor.SetAxisLabels(2, empty_str)

        # show labels
        if not show_xlabels:
            cube_axes_actor.SetAxisLabels(0, empty_str)

        if not show_ylabels:
            cube_axes_actor.SetAxisLabels(1, empty_str)

        if not show_zlabels:
            cube_axes_actor.SetAxisLabels(2, empty_str)

        # set font
        font_family = parse_font_family(font_family)
        for i in range(3):
            cube_axes_actor.GetTitleTextProperty(i).SetFontSize(font_size)
            cube_axes_actor.GetTitleTextProperty(i).SetColor(color)
            cube_axes_actor.GetTitleTextProperty(i).SetFontFamily(font_family)
            cube_axes_actor.GetTitleTextProperty(i).SetBold(bold)

            cube_axes_actor.GetLabelTextProperty(i).SetFontSize(font_size)
            cube_axes_actor.GetLabelTextProperty(i).SetColor(color)
            cube_axes_actor.GetLabelTextProperty(i).SetFontFamily(font_family)
            cube_axes_actor.GetLabelTextProperty(i).SetBold(bold)

        self.add_actor(cube_axes_actor, reset_camera=False)
        self.cube_axes_actor = cube_axes_actor

        if all_edges:
            self.add_bounding_box(color=color, corner_factor=corner_factor)

        if fmt is not None:
            cube_axes_actor.SetXLabelFormat(fmt)
            cube_axes_actor.SetYLabelFormat(fmt)
            cube_axes_actor.SetZLabelFormat(fmt)

        return cube_axes_actor