input: Write a python function to retrieve the content of a Wikipedia page given a query.
  assert get_wiki_page('Python (programming language)') is not None
  assert get_wiki_page('NonExistentPage') is None
output: def get_wiki_page(query):
      import requests
      
      url = f"https://en.wikipedia.org/w/api.php?action=query&format=json&prop=extracts&titles={query}&formatversion=2"
      response = requests.get(url)
      
      if response.status_code == 200:
          data = response.json()
          pages = data.get("query", {}).get("pages", [])
          if pages and "extract" in pages[0]:
              return pages[0]["extract"]
      
      return None