'Parses an HTML content and find links.'

def _parse_html(self, content):

    if (content is None):
        return None
    url_set = set()
    a_list = re.findall('<a.+href=[\\\'"]?([^\\\'"    >]+)', content)
    for a_href in a_list:
        url_set.add(a_href)
    img_list = re.findall('<img.+src=[\\\'"]?([^\\\'"    >]+)', content)
    for img_src in img_list:
        url_set.add(img_src)
    return url_set
