Fix the langchain chat pydantic bug

[SimFG]

#525

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[codecov]

Codecov Report

Merging #538 (18dae36) into dev (f9456aa) will decrease coverage by 0.99%.
Report is 2 commits behind head on dev.
The diff coverage is 83.95%.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #538      +/-   ##
==========================================
- Coverage   93.90%   92.91%   -0.99%     
==========================================
  Files          96       97       +1     
  Lines        4017     4249     +232     
==========================================
+ Hits         3772     3948     +176     
- Misses        245      301      +56     

Files Changed	Coverage Δ
gptcache/adapter/adapter.py	82.74% <ø> (-5.31%)	⬇️
gptcache/manager/scalar_data/manager.py	85.18% <33.33%> (-6.49%)	⬇️
gptcache/adapter/openai.py	81.57% <41.66%> (-13.05%)	⬇️
gptcache/manager/scalar_data/dynamo_storage.py	95.16% <95.16%> (ø)
gptcache/adapter/langchain_models.py	95.29% <100.00%> (+0.05%)	⬆️

... and 1 file with indirect coverage changes