@asyncio.coroutine<EOL><INDENT>def eth_sign(self, address, data):<DEDENT>
return (yield from self.rpc_call('<STR_LIT>', [address, data]))<EOL>
https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_sign

        :param address: Account address
        :type address: str

        :param data: Message to sign
        :type data: str

        :return: signature
        :rtype: str