input: Write a python function to fetch and print the HTML content of a given URL using the requests library.
  assert fetch_html('https://www.example.com/').startswith('<!doctype html>')
  assert fetch_html('https://www.example.com/').find('<title>Example Domain</title>') != -1
  assert fetch_html('https://www.example.com/').endswith('</html>')
output: import requests
  
  def fetch_html(url):
      response = requests.get(url)
      return response.text