code: func WithPeerFilter(value PeerFilter) copts.Opt {
  	return func(p copts.Params) {
  		logger.Debugf("Checking PeerFilter: %#+v", value)
  		if setter, ok := p.(peerFilterSetter); ok {
  			setter.SetPeerFilter(value)
  		}
  	}
  }
docs: // WithPeerFilter sets a peer filter which provides per-request filtering of peers