Scan the text and extract asset tags and links to corresponding
        files.

        @param text: Page text.
        @type text: str

        @return: @see CourseraOnDemand._extract_links_from_text

def _extract_links_from_asset_tags_in_text(self, text):
        """
        Scan the text and extract asset tags and links to corresponding
        files.

        @param text: Page text.
        @type text: str

        @return: @see CourseraOnDemand._extract_links_from_text
        """
        # Extract asset tags from instructions text
        asset_tags_map = self._extract_asset_tags(text)
        ids = list(iterkeys(asset_tags_map))
        if not ids:
            return {}

        # asset tags contain asset names and ids. We need to make another
        # HTTP request to get asset URL.
        asset_urls = self._extract_asset_urls(ids)

        supplement_links = {}

        # Build supplement links, providing nice titles along the way
        for asset in asset_urls:
            title = clean_filename(
                asset_tags_map[asset['id']]['name'],
                self._unrestricted_filenames)
            extension = clean_filename(
                asset_tags_map[asset['id']]['extension'].strip(),
                self._unrestricted_filenames)
            url = asset['url'].strip()
            if extension not in supplement_links:
                supplement_links[extension] = []
            supplement_links[extension].append((url, title))

        return supplement_links