input: Write a function to scrape photos and captions from a given website using Python. The function should take a URL as input and print the source URLs of the photos and their captions (if available). If no caption is available, it should print 'No caption'. If the input is an empty URL, it should return a message saying "No URL provided".
  assert scrape_photos_and_captions('https://example.com/webpage') == None
  assert scrape_photos_and_captions('') == "No URL provided"
output: def scrape_photos_and_captions(url):
      if not url:
          return "No URL provided"
      
      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.find_next('figcaption')
          if caption:
              print(f"Photo URL: {src}, Caption: {caption.text}")
          else:
              print(f"Photo URL: {src}, Caption: No caption")