<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def add_http_headers_for_attachment(response: HttpResponse, offered_filename: str = None, content_type: str = None, as_attachment: bool = False, as_inline: bool = False, content_length: int = None) -> None: """ Add HTTP headers to a Django response class object. Args: response: ``HttpResponse`` instance offered_filename: filename that the client browser will suggest content_type: HTTP content type as_attachment: if True, browsers will generally save to disk. If False, they may display it inline. http://www.w3.org/Protocols/rfc2616/rfc2616-sec19.html as_inline: attempt to force inline (only if not as_attachment) content_length: HTTP content length """

    if offered_filename is None:
        offered_filename = ''
    if content_type is None:
        content_type = 'application/force-download'
    response['Content-Type'] = content_type
    if as_attachment:
        prefix = 'attachment; '
    elif as_inline:
        prefix = 'inline; '
    else:
        prefix = ''
    fname = 'filename=%s' % smart_str(offered_filename)
    response['Content-Disposition'] = prefix + fname
    if content_length is not None:
        response['Content-Length'] = content_length