SyntaxWarning from invalid escape sequences in regex patterns (Python 3.12+)

[SR-Rubel]

While using nlpaug with Python 3.12, the following warning is raised due to invalid escape sequences in string literals used for regular expressions:

SyntaxWarning: invalid escape sequence '\s'
  prefix_reg = '(?<=\s|\W)'
SyntaxWarning: invalid escape sequence '\s'
  suffix_reg = '(?=\s|\W)'

These warnings originate from the context_word_embs.py file and are due to the use of unescaped backslashes in non-raw strings.

File Affected:
nlpaug/augmenter/word/context_word_embs.py, lines 123–124.

Why This Matters:

• Raw strings are the recommended way to write regular expressions in Python.
• Python 3.12+ raises SyntaxWarning for escape sequences that don’t have a clear meaning, and future versions may turn this into a SyntaxError.
• Fixing this improves compatibility and eliminates noisy warnings for users.