input: Write a python function to convert text to a URL-safe slug format.
  assert url_slug("Hello World!") == "hello-world"
  assert url_slug("Python is great") == "python-is-great"
  assert url_slug("Clean Code: A Handbook of Agile Software Craftsmanship") == "clean-code-a-handbook-of-agile-software-craftsmanship"
output: import re
  
  def url_slug(text):
      text = text.lower()
      text = re.sub(r'[^a-z0-9\s-]', '', text)
      text = re.sub(r'\s+', '-', text).strip('-')
      return text