sum() is replaced by itertools.chain.from_iterable()

[iedmrc]

sum() is the leanest method to flatten a string list, so it's been replaced by itertools.chain.from_iterable() . Please check #1830

[codecov-io]

Codecov Report

Merging #1831 into master will decrease coverage by 1.36%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1831      +/-   ##
==========================================
- Coverage   84.16%   82.79%   -1.37%     
==========================================
  Files          94       94              
  Lines       14185    14186       +1     
==========================================
- Hits        11939    11746     -193     
- Misses       2246     2440     +194

Impacted Files	Coverage Δ
transformers/tokenization_utils.py	91.22% <100%> (+0.02%)	⬆️
transformers/modeling_tf_pytorch_utils.py	9.85% <0%> (-83.1%)	⬇️
transformers/tests/modeling_tf_common_test.py	81.55% <0%> (-15.54%)	⬇️
transformers/modeling_roberta.py	59.41% <0%> (-12.36%)	⬇️
transformers/modeling_xlnet.py	71.18% <0%> (-2.44%)	⬇️
transformers/modeling_ctrl.py	94.24% <0%> (-2.22%)	⬇️
transformers/modeling_openai.py	80.66% <0%> (-1.34%)	⬇️

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[LysandreJik]

Looks good to me, thank you @iedmrc!

[thomwolf]

Great, thanks a lot @iedmrc!