code: def append_styles(self, tag, attrs):
          
          dattrs = dict(attrs)
          if 'class' in dattrs:
              #print "Found classes '%s'" % dattrs['class']
              class_names = dattrs['class'].split()
              dotted_names = map(prepend_dot,class_names)
              dotted_names.sort()
              self.used_classes.extend(' '.join(dotted_names))
              self.unchained_classes.extend(dotted_names)
          if 'id' in dattrs:
              #print "Found id '%s'" % dattrs['id']
              self.used_ids.extend(prepend_hash(dattrs['id'].strip()))
docs: Append classes found in HTML elements to the list of styles used.
          Because we haven't built the tree, we aren't using the `tag` parameter
          for now.
          @param <string> tag
              The HTML tag we're parsing
          @param <tuple> attrs
              A tuple of HTML element attributes such as 'class', 'id',
              'style', etc. The tuple is of the form ('html_attribute',
              'attr1', 'attr2', 'attr3' ... 'attrN')