docs: function ENS_0(provider, address) {
      // Ensures backwards compatibility
      if (provider.currentProvider) {
          provider = provider.currentProvider;
      }
  
      this.web3 = new Web3(provider);
      var registryContract = this.web3.eth.contract(registryInterface);
      if(address != undefined) {
        this.registryPromise = Promise.resolve(Promise.promisifyAll(registryContract.at(address)));
      } else {
        this.registryPromise = Promise.promisify(this.web3.version.getNetwork)().then(function(version) {
          return Promise.promisifyAll(registryContract.at(registryAddresses[version]));
        });
      }
  }