langchain-google: remove possible trailing newline from content text in response candidates

[aaronbriel]

PR Description

Renamed _strip_erroneous_spaces to _strip_erroneous_characters and added trailing newline removal, added unit tests for function.

Relevant issues

24648

Type

🐛 Bug Fix
🧹 Refactoring
✅ Test

Changes(optional)

Testing(optional)

make test

77 passed, 6 warnings in 0.82s

Note(optional)

[lkuligin]

PALM is going to be deprecated, do we really need this one?

[lkuligin]

actually, if your original issue was with gemini-1.5 model, I'm not sure this PR will fix it.

[aaronbriel]

@lkuligin Good catch. I've reverted the earlier code and instead added trailing newline removal to the content text of response candidates.

Before change:

>>> from langchain_google_genai import ChatGoogleGenerativeAI
>>> import os
>>> llm = ChatGoogleGenerativeAI(google_api_key=os.getenv('GOOGLE_API_KEY'), model='gemini-1.5-pro-002')
>>> prompt = "you are a football expert"
>>> text = "what is the name of the football team in Minnesota?"
>>> messages = [('system', prompt), ('human', text)]
>>> ai_msg = llm.invoke(messages)
>>> ai_msg.content
'The NFL team in Minnesota is the **Minnesota Vikings**.\n'

After change:

>>> from langchain_google_genai import ChatGoogleGenerativeAI
>>> import os
>>> llm = ChatGoogleGenerativeAI(google_api_key=os.getenv('GOOGLE_API_KEY'), model='gemini-1.5-pro-002')
>>> prompt = "you are a football expert"
>>> text = "what is the name of the football team in Minnesota?"
>>> messages = [('system', prompt), ('human', text)]
>>> ai_msg = llm.invoke(messages)
>>> ai_msg.content
'The NFL team in Minnesota is the **Minnesota Vikings**.'

[aaronbriel]

@lkuligin are you able to approve this PR or is there someone else to tag?

[adamJLev]

waiting for this fix too, thanks for the PR 👌🏼