fix wrong type annotations and nonexistent types

[stydxm]

• The code shown in the document cause warnings in the IDE.
  

• ragas.llms.LangchainLLM is no longer exists but from ragas.llms import LangchainLLM is still left in document

First time here, apology for any mistakes.

[shahules786]

Hey @stydxm , thanks for the work.
@jjmachan shouldn't these classes work in ragas without explicitly wrapping LangchainLLMwrapper due to this line

[stydxm]

Hey @stydxm , thanks for the work. @jjmachan shouldn't these classes work in ragas without explicitly wrapping LangchainLLMwrapper due to this line

Sorry I didn't noticed that. That PR was merged after I found this problem and start working on it yesterday 😂.
However the problem in gcp-vertexai.ipynb still exists, please allow me minutes to edit it.

[shahules786]

@stydxm Thanks buddy :)

[stydxm]

@stydxm Thanks buddy :)

Done

[jjmachan]

wow thank you so much for updating this @stydxm 🙂
welcome to the contributor list 🎉