import re


def group_tag(string):
    """Extract group tag."""

    left_br = '><!-- '
    right_br = ' <=< ACCEPT -->'
    accept = re.search(left_br + '.+' + right_br, string)
    if not accept:
        return ''
    return re.sub(left_br, '', re.sub(right_br, '', accept.group(0)))