input: Write a function to scrape photos and captions from a given website. The function should take a website URL as input, retrieve the HTML content, parse it using BeautifulSoup, and print the source URL of each photo along with its caption if available.
  assert scrape_photos_and_captions('https://example.com/webpage') == None
  assert scrape_photos_and_captions('https://example.com/differentpage') == 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'):
          src = img.get('src')
          caption = img.get('alt')
          print(f"Source URL: {src}, Caption: {caption}")