input: Write a function to scrape photos and captions from a given website. The function should take a URL as input, download the webpage's HTML, parse it to extract all images and their corresponding captions within a specified div, and print the photo URL and its caption if available.
  assert scrape_photos_and_captions('https://example.com/webpage')==None
output: def scrape_photos_and_captions(url):
      import requests
      from bs4 import BeautifulSoup
      
      response = requests.get(url)
      soup = BeautifulSoup(response.text, 'html.parser')
      
      for img in soup.find_all('img'):
          caption = img.find_next('div', {'class': 'caption'})
          print(img['src'], caption.text if caption else '')