code: def set_style(key):
      
      if key is None:
          return
      elif not key or key in ['unset', 'backup']:
          if 'backup' in styles:
              plt.rcParams.update(styles['backup'])
          else:
              raise Exception('No style backed up to restore')
      elif key not in styles:
          raise KeyError('%r not in available styles.')
      else:
          path = os.path.join(os.path.dirname(__file__), styles[key])
          new_style = rc_params_from_file(path, use_default_template=False)
          styles['backup'] = dict(plt.rcParams)
  
          plt.rcParams.update(new_style)
docs: Select a style by name, e.g. set_style('default'). To revert to the
      previous style use the key 'unset' or False.