vertexai: handle messages that evaluate to a literal float

[JoshuaPostel]

PR Description

the function _convert_to_parts(message: BaseMessage) throws an error when the message passed gets evaluated to a float. Example error:

...

  File "/XXX/.venv/lib/python3.10/site-packages/langchain_google_vertexai/chat_models.py", line 313, in _parse_chat_history_gemini                                             
    parts = _convert_to_parts(message)                                                                                                                                                                             
            │                 └ HumanMessage(content='3.5', additional_kwargs={}, response_metadata={})                                                                                                            
            └ <function _parse_chat_history_gemini.<locals>._convert_to_parts at 0x167677d90>                                                                                                                      
  File "/XXX/.venv/lib/python3.10/site-packages/langchain_google_vertexai/chat_models.py", line 280, in _convert_to_parts                                                      
    for raw_part in raw_content:                                                                                                                                                                                   
                    └ 3.5   

TypeError: 'float' object is not iterable

Relevant issues

None

Type

🐛 Bug Fix

[SYED-M-HUSSAIN]

if isinstance(raw_content, (int, float, str)):
    raw_content = [str(raw_content)]
elif isinstance(raw_content, list):
    raw_content = [str(item) for item in raw_content]
else:
    raise TypeError(f"Unsupported type: {type(raw_content)}")

This version merges the first two conditions into one, as both involve converting the value to a string and wrapping it in a list.

[JoshuaPostel]

@SYED-M-HUSSAIN are you requesting I apply these changes to this PR?