docs: def analyze_internal_angles(self, return_plot=False):
          """Analyze the internal angles of the grid. Angles shouldn't be too
          small because this can cause problems/uncertainties in the
          Finite-Element solution of the forward problem. This function prints
          the min/max values, as well as quantiles, to the command line, and can
          also produce a histogram plot of the angles.
  
          Parameters
          ----------
          return_plot: bool
              if true, return (fig, ax) objects of the histogram plot
  
          Returns
          -------
          fig: matplotlib.figure
              figure object
          ax: matplotlib.axes
              axes object
  
          Examples
          --------
  
              >>> import crtomo.grid as CRGrid
                  grid = CRGrid.crt_grid()
                  grid.load_elem_file('elem.dat')
                  fig, ax = grid.analyze_internal_angles(Angles)
              This grid was sorted using CutMcK. The nodes were resorted!
              Triangular grid found
              Minimal angle: 22.156368696965796 degrees
              Maximal angle: 134.99337326279496 degrees
              Angle percentile 10%: 51.22 degrees
              Angle percentile 20%: 55.59 degrees
              Angle percentile 30%: 58.26 degrees
              Angle percentile 40%: 59.49 degrees
              Angle percentile 50%: 59.95 degrees
              Angle percentile 60%: 60.25 degrees
              Angle percentile 70%: 61.16 degrees
              Angle percentile 80%: 63.44 degrees
              Angle percentile 90%: 68.72 degrees
              generating plot...
              >>> # save to file with
                  fig.savefig('element_angles.png', dpi=300)
  
          """
          angles = self.get_internal_angles().flatten()
  
          print('Minimal angle: {0} degrees'.format(np.min(angles)))
          print('Maximal angle: {0} degrees'.format(np.max(angles)))
          # print out quantiles
          for i in range(10, 100, 10):
              print('Angle percentile {0}%: {1:0.2f} degrees'.format(
                  i,
                  np.percentile(angles, i),
              ))
  
          if return_plot:
              print('generating plot...')
              fig, ax = plt.subplots(1, 1, figsize=(12 / 2.54, 8 / 2.54))
              ax.hist(angles, int(angles.size / 10))
              ax.set_xlabel('angle [deg]')
              ax.set_ylabel('count')
              fig.tight_layout()
              # fig.savefig('plot_element_angles.jpg', dpi=300)
              return fig, ax