This callback is called form the Crazyflie API when a Crazyflie
        has been connected and the TOCs have been downloaded.

def _connected(self, link_uri):
        """ This callback is called form the Crazyflie API when a Crazyflie
        has been connected and the TOCs have been downloaded."""
        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('')