input: Write a function to extract titles of all YouTube videos from a given URL. The function should return a list of video titles or an empty list if no titles are found. Use regular expressions to match the video titles in the HTML content of the URL. If the URL is invalid or the page cannot be accessed, return an empty list.
  assert extract_youtube_titles("https://www.youtube.com/user/Thexvid/videos") == ["video title 1", "video title 2"]
  assert extract_youtube_titles("https://www.youtube.com/user/nonexistentchannel/videos") == []
  assert extract_youtube_titles("") == []
  assert extract_youtube_titles("https://www.invalidurl.com") == []
output: import re
  import requests
  
  def extract_youtube_titles(url):
      try:
          response = requests.get(url)
          response.raise_for_status()
          html_content = response.text
          titles = re.findall(r'"title":{"runs":\[{"text":"([^"]+)"', html_content)
          return titles
      except:
          return []