input: Write a python function to extract all the links from a given webpage.
  assert extract_links('https://www.example.com')==['https://www.iana.org/domains/example']
  assert extract_links('https://www.w3schools.com')==['https://www.w3schools.com/']
  assert extract_links('https://www.python.org')==['https://www.python.org/about/', 'https://www.python.org/doc/', 'https://www.python.org/downloads/']
output: def extract_links(url):
      import requests
      from bs4 import BeautifulSoup
      
      response = requests.get(url)
      soup = BeautifulSoup(response.text, 'html.parser')
      links = [a.get('href') for a in soup.find_all('a', href=True)]
      return links