code: func (c *Client) RegisterBlockEvent(filter ...fab.BlockFilter) (fab.Registration, <-chan *fab.BlockEvent, error) {
  	return c.eventService.RegisterBlockEvent(filter...)
  }
docs: // RegisterBlockEvent registers for block events. If the caller does not have permission
  // to register for block events then an error is returned. Unregister must be called when the registration is no longer needed.
  //  Parameters:
  //  filter is an optional filter that filters out unwanted events. (Note: Only one filter may be specified.)
  //
  //  Returns:
  //  the registration and a channel that is used to receive events. The channel is closed when Unregister is called.