Python write_stream sample returns AttributeError when run

通过使用文档中所述的 Docker 命令启动服务器后运行 write_stream.py 来复现故障，然后将其与 list_streams.py 进行比较。检查 write_stream.py 中的流查找，并验证示例所预期的流设置。完成的标准是：示例能够在全新的服务器上运行，或清楚记录所需的设置且不会出现 AttributeError。

Hi,

I am running a local timebase server using docker using the following command:

docker run --rm -d -p 8011:8011 --name=timebase-server --ulimit nofile=65536:65536 finos/timebase-ce-server:6.1

This allows me to run the list_streams.py sample successfully.

However, when I run the write_stream.py sample I get the following error:

Connected to dxtick://localhost:8011
Connection dxtick://localhost:8011 closed.
Traceback (most recent call last):
  File "write_stream.py", line 28, in <module>
    loader = stream.createLoader(tbapi.LoadingOptions())
AttributeError: 'NoneType' object has no attribute 'createLoader'

A cursory look at the code leads me to believe that the bitfinex stream does not exist in the timebase server so the person who wrote this sample was probably pointing to a timebase server that had already been primed in some way. So this sample does not stand by itself and needs some unknown setup.

I have attempted to create a stream instead of opening it but I get further errors due to the stream not being setup correctly (as expected):

No message types defined for stream at DxApiImpl::TickLoaderImpl *DxApiImpl::TickLoaderImpl::open(

I hope that is enough info to reproduce.