code: func (df EgressDigestFilter) byContext() algo.DigestFilter {
  	return func(context interface{}) func(digestItem string) bool {
  		return func(digestItem string) bool {
  			return df(context.(proto.ReceivedMessage))(digestItem)
  		}
  	}
  }
docs: // byContext converts this EgressDigFilter to an algo.DigestFilter