class Sass::Selector::Pseudo

def to_s(opts = {})
  # :not() is a special case, because :not(<nothing>) should match
  # everything.
  return '' if name == 'not' && @selector && @selector.members.all? {|m| m.invisible?}
  res = (syntactic_type == :class ? ":" : "::") + @name
  if @arg || @selector
    res << "("
    res << Sass::Util.strip_except_escapes(@arg) if @arg
    res << " " if @arg && @selector
    res << @selector.to_s(opts) if @selector
    res << ")"
  end
  res
end