fix: process Vertex AI response properly for usage#1173

t-miyak wants to merge 7 commits intolangfuse:mainlangfuse/langfuse-python:mainfrom

t-miyak:feature/correspond-to-vertexai-chat-llm-resultt-miyak/langfuse-python:feature/correspond-to-vertexai-chat-llm-resultCopy head branch name to clipboard