多轮对话（流式）

curl --location --request POST 'https://llm-api.mmchat.xyz/gemini/v1beta/models/gemini-2.5-flash-preview-05-20:streamGenerateContent?alt=sse&key=METACHAT_API_KEY' \
--header 'Content-Type: application/json' \
--data-raw '{
    "contents": [
      {
        "role": "user",
        "parts": [
          {
            "text": "Hello"
          }
        ]
      },
      {
        "role": "model",
        "parts": [
          {
            "text": "Great to meet you. What would you like to know?"
          }
        ]
      },
      {
        "role": "user",
        "parts": [
          {
            "text": "I have two dogs in my house. How many paws are in my house?"
          }
        ]
      }
    ]
  }'