code: def check_known_elements(self):
          
          domain = self.get_clean_domain()
          if domain in self.custom_site_mapping.keys():
              classes = self.custom_site_mapping.get(domain).split('|')
              for classname in classes:
                  KNOWN_IMG_DOM_NAMES.append(classname)
  
          image = None
          doc = self.article.raw_doc
  
          def _check_elements(elements):
              image = None
              for element in elements:
                  tag = self.parser.getTag(element)
                  if tag == 'img':
                      image = element
                      return image
                  else:
                      images = self.parser.getElementsByTag(element, tag='img')
                      if images:
                          image = images[0]
                          return image
              return image
  
          # check for elements with known id
          for css in KNOWN_IMG_DOM_NAMES:
              elements = self.parser.getElementsByTag(doc, attr="id", value=css)
              image = _check_elements(elements)
              if image is not None:
                  src = self.parser.getAttribute(image, attr='src')
                  if src:
                      return self.get_image(image, src, score=90, extraction_type='known')
  
          # check for elements with known classes
          for css in KNOWN_IMG_DOM_NAMES:
              elements = self.parser.getElementsByTag(doc, attr='class', value=css)
              image = _check_elements(elements)
              if image is not None:
                  src = self.parser.getAttribute(image, attr='src')
                  if src:
                      return self.get_image(image, src, score=90, extraction_type='known')
  
          return None
docs: \
          in here we check for known image contains from sites
          we've checked out like yahoo, techcrunch, etc... that have
          * known  places to look for good images.
          * TODO: enable this to use a series of settings files
            so people can define what the image ids/classes
            are on specific sites