makeSelf = (proto, instanceCount) => {
  const self = create(proto);
  if (LABEL_INSTANCES) {
    defineProperty(self, Symbol.toStringTag, {
      value: `${proto[Symbol.toStringTag]}#${instanceCount}`,
      writable: false,
      enumerable: false,
      configurable: false,
    });
  }
  return harden(self);
}
@template {{}} T
@param {T} proto
@param {number} instanceCount
@returns {T}