static setRegistries(regs) {
		if (!Array.isArray(regs)) regs = [regs];
		regs.forEach(reg => {
			if (!(reg instanceof Registry)) {
				throw new TypeError(`Expected Registry, got ${typeof reg}`);
			}
		});
		registries = regs;
	}
Sets the registry or registries to be aggregated. Call from workers to
use a registry/registries other than the default global registry.
@param {Array<Registry>|Registry} regs Registry or registries to be
  aggregated.
@return {void}