code: def check_islands(self, show_info=False):
          
          if not hasattr(self, 'Line'):
              logger.error('<Line> device not found.')
              return
          self.Line.connectivity(self.Bus)
  
          if show_info is True:
  
              if len(self.Bus.islanded_buses) == 0 and len(
                      self.Bus.island_sets) == 0:
                  logger.debug('System is interconnected.')
              else:
                  logger.info(
                      'System contains {:d} islands and {:d} islanded buses.'.
                      format(
                          len(self.Bus.island_sets),
                          len(self.Bus.islanded_buses)))
  
              nosw_island = []  # no slack bus island
              msw_island = []  # multiple slack bus island
              for idx, island in enumerate(self.Bus.island_sets):
                  nosw = 1
                  for item in self.SW.bus:
                      if self.Bus.uid[item] in island:
                          nosw -= 1
                  if nosw == 1:
                      nosw_island.append(idx)
                  elif nosw < 0:
                      msw_island.append(idx)
  
              if nosw_island:
                  logger.warning(
                      'Slack bus is not defined for {:g} island(s).'.format(
                          len(nosw_island)))
              if msw_island:
                  logger.warning(
                      'Multiple slack buses are defined for {:g} island(s).'.
                      format(len(nosw_island)))
  
              if (not nosw_island) and (not msw_island):
                  logger.debug(
                      'Each island has a slack bus correctly defined.')
docs: Check the connectivity for the ac system
  
          Parameters
          ----------
          show_info : bool
              Show information when the system has islands. To be used when
              initializing power flow.
  
          Returns
          -------
          None