def fromWeb3(cls, web3, addr=None):
        """
        Generate an ENS instance with web3

        :param `web3.Web3` web3: to infer connection information
        :param hex-string addr: the address of the ENS registry on-chain. If not provided,
            ENS.py will default to the mainnet ENS registry address.
        """
        return cls(web3.manager.provider, addr=addr)