[*.py] Rename "Arguments:" to "Args:"

[SamuelMarks]

I've written custom parsers and emitters for everything from docstrings to classes and functions. However, I recently came across an issue when I was parsing/generating from the TensorFlow—and now PyTorch—codebases: inconsistent use of Args: and Arguments: in its docstrings. It is easy enough to extend my parsers to support both variants, however it looks like Arguments: is wrong anyway, as per:

• https://google.github.io/styleguide/pyguide.html#doc-function-args @ ddccc0f

• https://chromium.googlesource.com/chromiumos/docs/+/master/styleguide/python.md#describing-arguments-in-docstrings @ 9fc0fc0

• https://sphinxcontrib-napoleon.readthedocs.io/en/latest/example_google.html @ c0ae8e3

Therefore, only Args: is valid. This PR replaces them throughout the codebase.

PS: For related PRs, see pytorch/pytorch/pull/49736

[codecov]

Codecov Report

Merging #1110 (6998654) into master (479d58f) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1110   +/-   ##
=======================================
  Coverage   77.54%   77.54%           
=======================================
  Files          45       45           
  Lines        3086     3086           
=======================================
  Hits         2393     2393           
  Misses        693      693           

Impacted Files	Coverage Δ
torchtext/data/dataset.py	93.82% <ø> (ø)
torchtext/data/field.py	92.83% <ø> (ø)
torchtext/data/functional.py	89.47% <ø> (ø)
torchtext/data/iterator.py	62.66% <ø> (ø)
torchtext/data/metrics.py	100.00% <ø> (ø)
torchtext/data/pipeline.py	100.00% <ø> (ø)
torchtext/data/utils.py	71.92% <ø> (ø)
torchtext/datasets/imdb.py	48.38% <ø> (ø)
torchtext/datasets/language_modeling.py	90.38% <ø> (ø)
torchtext/datasets/nli.py	49.29% <ø> (ø)
... and 20 more

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[zhangguanheng66]

Let's wait and see progress of the PR in pytorch core library.

[zhangguanheng66]

A similar PR to pytorch has been merged. Ready to go.