input: Write a function to extract text content from a given URL.
  assert extract_text("https://www.example.com")[:15] == b'<!doctype html>'
  assert extract_text("https://www.w3.org/TR/PNG/iso_8859-1.txt")[:15] == b'The following '
  assert extract_text("https://www.python.org")[:15] == b'<!doctype html>'
output: def extract_text(url):
      import requests
      response = requests.get(url)
      return response.content