fixes for pydantic in gpt_langchain.py

[one-lithe-rune]

Motivation

Just before a686d7d which temporarily disabled DocuChat/langchain I was getting the following error, when running the ui/web after manually installing the langchain dependency:

Traceback (most recent call last):
  File "C:\develop\SHARK\apps\stable_diffusion\web\index.py", line 94, in <module>
    from apps.stable_diffusion.web.ui.utils import create_custom_models_folders
  File "C:\develop\SHARK\apps\stable_diffusion\web\ui\__init__.py", line 82, in <module>
    from apps.stable_diffusion.web.ui.h2ogpt import h2ogpt_upload, h2ogpt_web
  File "C:\develop\SHARK\apps\stable_diffusion\web\ui\h2ogpt.py", line 15, in <module>
    from gpt_langchain import (
  File "C:\develop\SHARK\apps\language_models\langchain\gpt_langchain.py", line 418, in <module>
    class GradioInference(LLM):
  File "pydantic\main.py", line 186, in pydantic.main.ModelMetaclass.__new__
  File "pydantic\utils.py", line 167, in pydantic.utils.validate_field_name

NameError: Field name "stream" shadows a BaseModel attribute; use a different field name with "alias='stream'".

Possibly DNM, because I don't know how relevant this is in real life.

Changes

• Follow the advice in the above error and change 'stream' instance variables to 'stream_output' and aliased them back to 'stream' to clear clash with Pydantic BaseModel.

Problems/Concerns

• May not be relevant with this disabled.
• May have been a dependency issue on my part.
• My first use of pydantic was on an internal work project today, so I'm not familiar with it at all.

[powderluv]

@vivekkhandelwal1 please review if we need this

[vivekkhandelwal1]

@vivekkhandelwal1 please review if we need this

Sure, I will first locally test this patch and then review it.

[vivekkhandelwal1]

LGTM