docs: function validatePacket(type, packet, fn) {
          debug('Type:', type);
          debug('Packet:', packet);
  
          if (!tv4.validate(packet, defaultSchemas[type])) {
              return fn(tv4.error);
          }
  
          if (packet.hasOwnProperty('provider') && !validUUID(packet.provider)) {
              return fn(new Error('`provider` must be a valid UUID'));
          }
  
          if (packet.hasOwnProperty('t') && !validTimestamp(packet.t)) {
              return fn(new Error('`t` must ba an ISO 8601 timestamp'));
          }
  
          return fn(null, true);
      }