input: Write a python function to generate HTML listing from a list of dictionaries.
  assert ListingGenerator([{"title": "Title1", "description": "Description1", "link": "http://link1.com"}, {"title": "Title2", "description": "Description2", "link": "http://link2.com"}]).generate_listing() == '<div class="listing">\n    <h3>Title1</h3>\n    <p>Description1</p>\n    <p><a href="http://link1.com">READ MORE</a></p>\n    <h3>Title2</h3>\n    <p>Description2</p>\n    <p><a href="http://link2.com">READ MORE</a></p>\n</div>'
  assert ListingGenerator([]).generate_listing() == '<div class="listing">\n</div>'
  assert ListingGenerator([{"title": "OnlyTitle", "description": "OnlyDescription", "link": "http://onlylink.com"}]).generate_listing() == '<div class="listing">\n    <h3>OnlyTitle</h3>\n    <p>OnlyDescription</p>\n    <p><a href="http://onlylink.com">READ MORE</a></p>\n</div>'
output: class ListingGenerator:
      def __init__(self, data):
          self.data = data
  
      def generate_listing(self):
          html = '<div class="listing">\n'
          for item in self.data:
              html += f'    <h3>{item["title"]}</h3>\n'
              html += f'    <p>{item["description"]}</p>\n'
              html += f'    <p><a href="{item["link"]}">READ MORE</a></p>\n'
          html += '</div>'
          return html