code: def _connected(self, link_uri):
          
          print('Connected to %s' % link_uri)
  
          # Print the param TOC
          p_toc = self._cf.param.toc.toc
          for group in sorted(p_toc.keys()):
              print('{}'.format(group))
              for param in sorted(p_toc[group].keys()):
                  print('\t{}'.format(param))
                  self._param_check_list.append('{0}.{1}'.format(group, param))
              self._param_groups.append('{}'.format(group))
              # For every group, register the callback
              self._cf.param.add_update_callback(group=group, name=None,
                                                 cb=self._param_callback)
  
          # You can also register a callback for a specific group.name combo
          self._cf.param.add_update_callback(group='cpu', name='flash',
                                             cb=self._cpu_flash_callback)
  
          print('')
docs: This callback is called form the Crazyflie API when a Crazyflie
          has been connected and the TOCs have been downloaded.