input: Writer a function to extract the titles of all YouTube videos from a given URL using Python. The function should return a list of video titles.
  
  assert extract_youtube_titles("https://www.youtube.com/user/Thexvid/videos")==['50 Life Hacks to Look Like a Genius', '13 Cool Gadgets and Tools You Didn’t Know Existed', '15 Awesome Everyday Items You Can Make Easily', '10 Amazing Inventions You Must See', '10 Secret Inventions You Didn\u2019t Know Existed']
  assert extract_youtube_titles("https://www.youtube.com/c/mkbhd/videos")==['One Phone Too Many | Huawei Nova 7 SE', 'The MacBook Wars', 'My Friend Giorgio Armani', 'Why Your Next Phone Will Be Underwater', 'I Streamed 16 Phones For 12 Hours...']
  assert extract_youtube_titles("https://www.youtube.com/user/PewDiePie/videos")==[]
  
  import requests
  import re
  
  def extract_youtube_titles(url):
      r = requests.get(url)
      titles = re.findall('<a href="/watch\?v=([^"]+)">(.+?)<\/a>', r.content.decode('utf-8'))
      return [title[1] for title in titles]
output: import requests
  import re
  
  def extract_youtube_titles(url):
      r = requests.get(url)
      titles = re.findall('<a href="/watch\?v=([^"]+)">(.+?)<\/a>', r.content.decode('utf-8'))
      return [title[1] for title in titles]