problem of wrong calculation of data-flow match score

[ZeyuTeng96]

As microsoft/CodeXGLUE#152

I found the same problem for data-flow score calculation as addressed on the above in line 121 and 122 https://github.com/k4black/codebleu/blob/main/codebleu/dataflow_match.py#L121C40-L121C44

There are two possible way to solve it:

1. using list.extend or append func to add nodes
2. adding a sorted() func to it

Do you think is it feasible? I am willing to make a PR to fix the issue

[ZeyuTeng96]

@k4black Hello Sir. Is that possible to do it?