@asyncio.coroutine<EOL><INDENT>def web3_sha3(self, data):<DEDENT>
data = add_0x(binascii.hexlify(str(data).encode('<STR_LIT:utf-8>')))<EOL>return (yield from self.rpc_call('<STR_LIT>', [data]))<EOL>
https://github.com/ethereum/wiki/wiki/JSON-RPC#web3_sha3

        :param data: Data for hashing
        :type data: str

        :return: Keccak-256
        :rtype: str