Why s and n are removed in extended charset_type ?

[thiago-figueredo]

In cyclic_pattern_charset function, the s and n are removed in charset[1] and added in charset[2]. Why this happen ?

charset = []
charset += ["ABCDEFGHIJKLMNOPQRSTUVWXYZ"] # string.uppercase
charset += ["abcdefghijklmnopqrstuvwxyz"] # string.lowercase
charset += ["0123456789"] # string.digits

if not charset_type:
    charset_type = config.Option.get("pattern")
if charset_type == 1: # extended type
    charset[1] = "%$-;" + re.sub("[sn]", "", charset[1])
    charset[2] = "sn()" + charset[2]