  original implementation trains on SQuAD with padding on the left, therefore the padding defaults are set to left.
Transformer-XL is one of the few models that has no sequence length limit.
This model was contributed by thomwolf. The original code can be found here.
TransformerXL does not work with torch.nn.DataParallel due to a bug in PyTorch, see issue #36035
TransfoXLConfig
[[autodoc]] TransfoXLConfig
TransfoXLTokenizer
[[autodoc]] TransfoXLTokenizer
    - save_vocabulary
TransfoXL specific outputs
[[autodoc]] models.transfo_xl.modeling_transfo_xl.TransfoXLModelOutput
[[autodoc]] models.transfo_xl.modeling_transfo_xl.TransfoXLLMHeadModelOutput
[[autodoc]] models.transfo_xl.modeling_tf_transfo_xl.TFTransfoXLModelOutput
[[autodoc]] models.transfo_xl.modeling_tf_transfo_xl.TFTransfoXLLMHeadModelOutput
