异步 Chromium
Chromium 是 Playwright 支持的浏览器之一，Playwright 是一个用于控制浏览器自动化的库。
通过运行p.chromium.launch(headless=True)，我们正在启动一个无头模式的Chromium实例。
无头模式意味着浏览器在没有图形用户界面的情况下运行。
在下面的示例中，我们将使用AsyncChromiumLoader来加载页面，然后使用Html2TextTransformer来去除HTML标签和其他语义信息。
%pip install --upgrade --quiet playwright beautifulsoup4 html2text
!playwright install
注意： 如果您正在使用 Jupyter 笔记本，您可能还需要在加载文档之前安装并应用 nest_asyncio，如下所示：
!pip install nest-asyncio
import nest_asyncio
nest_asyncio.apply()
from langchain_community.document_loaders import AsyncChromiumLoader
urls = ["https://docs.smith.langchain.com/"]
loader = AsyncChromiumLoader(urls, user_agent="MyAppUserAgent")
docs = loader.load()
docs[0].page_content[0:100]
API Reference:AsyncChromiumLoader
'<!DOCTYPE html><html lang="en" dir="ltr" class="docs-wrapper docs-doc-page docs-version-2.0 plugin-d'
现在让我们使用转换器将文档转换为更易读的语法：
from langchain_community.document_transformers import Html2TextTransformer
html2text = Html2TextTransformer()
docs_transformed = html2text.transform_documents(docs)
docs_transformed[0].page_content[0:500]
API Reference:Html2TextTransformer
'Skip to main content\n\nGo to API Docs\n\nSearch`⌘``K`\n\nGo to App\n\n * Quick start\n * Tutorials\n\n * How-to guides\n\n * Concepts\n\n * Reference\n\n * Pricing\n * Self-hosting\n\n * LangGraph Cloud\n\n * * Quick start\n\nOn this page\n\n# Get started with LangSmith\n\n**LangSmith** is a platform for building production-grade LLM applications. It\nallows you to closely monitor and evaluate your application, so you can ship\nquickly and with confidence. Use of LangChain is not necessary - LangSmith\nworks on it'