https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_getcode

        :param address: Address of contract
        :type address: str

        :param block: Block tag or number (optional)
        :type block: int or BLOCK_TAGS

        :return: code
        :rtype: str

def eth_getCode(self, address, block=BLOCK_TAG_LATEST):
        """https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_getcode

        :param address: Address of contract
        :type address: str

        :param block: Block tag or number (optional)
        :type block: int or BLOCK_TAGS

        :return: code
        :rtype: str
        """
        block = validate_block(block)
        return (yield from self.rpc_call('eth_getCode', [address, block]))