docs: def reload_core(host=None, core_name=None):
      '''
      MULTI-CORE HOSTS ONLY
      Load a new core from the same configuration as an existing registered core.
      While the "new" core is initializing, the "old" one will continue to accept
      requests. Once it has finished, all new request will go to the "new" core,
      and the "old" core will be unloaded.
  
      host : str (None)
          The solr host to query. __opts__['host'] is default.
      core_name : str
          The name of the core to reload
  
      Return : dict<str,obj>::
  
          {'success':boolean, 'data':dict, 'errors':list, 'warnings':list}
  
      CLI Example:
  
      .. code-block:: bash
  
          salt '*' solr.reload_core None music
  
      Return data is in the following format::
  
          {'success':bool, 'data':dict, 'errors':list, 'warnings':list}
      '''
      ret = _get_return_dict()
      if not _check_for_cores():
          err = ['solr.reload_core can only be called by "multi-core" minions']
          return ret.update({'success': False, 'errors': err})
  
      if _get_none_or_value(core_name) is None and _check_for_cores():
          success = True
          for name in __opts__['solr.cores']:
              resp = reload_core(host, name)
              if not resp['success']:
                  success = False
              data = {name: {'data': resp['data']}}
              ret = _update_return_dict(ret, success, data,
                      resp['errors'], resp['warnings'])
          return ret
      extra = ['action=RELOAD', 'core={0}'.format(core_name)]
      url = _format_url('admin/cores', host=host, core_name=None, extra=extra)
      return _http_request(url)