Temp fix

[lkuligin]

fixed #49

[eycjur]

@lkuligin
Thank you for the correction. But i think this fix is ​​not enough. This is because assertCountEqual does not determine the contents of nested dictionaries (I don't know if this is normal behavior for assertCountEqual, but at least it behaves like that)

For example, the following test will pass

from unittest import TestCase

def test_assert_count_equal():
	TestCase().assertCountEqual(
		{
			"stream": False,
			"safety_settings": None,
			"generation_config": {
				"max_output_tokens": 1,
				"temperature": 0,
				"top_k": 10,
				"top_p": 0.5,
				"stop_sequences": None,
			},
		},
		{
			"stream": False,
			"safety_settings": None,
			"generation_config": {
			},
		}
	)

And in the case of this pull request, I think it is necessary to modify the line below.

libs/vertexai/langchain_google_vertexai/llms.py
            default_value = default_params.get(param_name)
-             if param_value or default_value:
+             if param_value is not None or default_value is not None:
                updated_params[param_name] = (
                    param_value if param_value is not None else default_value
                )
        return updated_params

Thanks!

[lkuligin]

@eycjur it's embarassing for me, but you're right! thanks a lot for spotting it. Fixed.

P.S. Please, feel free to contribute yourself next time, we welcome contributions very much!

[eycjur]

@lkuligin
I've learned a lot from your code, so I'm glad I could help you out!
Your comments are very encouraging. Please let me contribute next time!