input: Write a function to scrape photos and captions from a given website using BeautifulSoup and requests libraries. The function should take a URL as input, fetch the HTML content from that URL, parse the HTML to find all images and their associated captions, and then print each photo's URL along with its caption or indicate if there is no caption. If no images or captions are found, print a message indicating that.
  
  
  def scrape_photos_and_captions(url):
      from bs4 import BeautifulSoup
      import requests
      
      # Get the HTML source code
      req = requests.get(url)
      html = req.text
      
      # Parse HTML source and extract photo and caption
      soup = BeautifulSoup(html, features='lxml')
      image_divs = soup.find_all('div', {'class': 'image-gallery__image'})
      
      if not image_divs:
          print("No images or captions found.")
          return
      
      for image_div in image_divs:
          figure = image_div.find('figure')
          src = figure.find('img')['src']
          caption = figure.find('figcaption')
          print('Photo: ', src)
          if caption:
              print('Caption: ', caption.text)
          else:
              print('No caption')
          print('\n')
  
  assert scrape_photos_and_captions('https://example.com/webpage') # Expected output: Photo URLs and captions or 'No images or captions found.'
  
output: def scrape_photos_and_captions(url):
      from bs4 import BeautifulSoup
      import requests
      
      req = requests.get(url)
      html = req.text
      
      soup = BeautifulSoup(html, features='lxml')
      image_divs = soup.find_all('div', {'class': 'image-gallery__image'})
      
      if not image_divs:
          print("No images or captions found.")
          return
      
      for image_div in image_divs:
          figure = image_div.find('figure')
          src = figure.find('img')['src']
          caption = figure.find('figcaption')
          print('Photo: ', src)
          if caption:
              print('Caption: ', caption.text)
          else:
              print('No caption')
          print('\n')