code: def set_background(self, color, loc='all'):
          
          if color is None:
              color = rcParams['background']
          if isinstance(color, str):
              if color.lower() in 'paraview' or color.lower() in 'pv':
                  # Use the default ParaView background color
                  color = PV_BACKGROUND
              else:
                  color = vtki.string_to_rgb(color)
  
          if loc =='all':
              for renderer in self.renderers:
                  renderer.SetBackground(color)
          else:
              renderer = self.renderers[self.loc_to_index(loc)]
              renderer.SetBackground(color)
docs: Sets background color
  
          Parameters
          ----------
          color : string or 3 item list, optional, defaults to white
              Either a string, rgb list, or hex color string.  For example:
                  color='white'
                  color='w'
                  color=[1, 1, 1]
                  color='#FFFFFF'
  
          loc : int, tuple, list, or str, optional
              Index of the renderer to add the actor to.  For example,
              ``loc=2`` or ``loc=(1, 1)``.  If ``loc='all'`` then all
              render windows will have their background set.