human
Solve the following python programming problem given the following code:
@ classmethod 
def _traverse_options(cls, obj, opt_type, opts, specs = None, keyfn = None, defaults = True) : 
    '
        Traverses the supplied object getting all options in opts for
        the specified opt_type and specs. Also takes into account the
        plotting class defaults for plot options. If a keyfn is
        supplied the returned options will be grouped by the returned
        keys.
        ' 
    def lookup(x) : 
        '
            Looks up options for object, including plot defaults,
            keyfn determines returned key otherwise None key is used.
            ' 
        options = cls.lookup_options (x, opt_type) 
        selected = { o : options.options [o] for o in opts if (o in options.options) } 
        if ((opt_type == 'plot') and defaults) : 
            plot = Store.registry [cls.renderer.backend].get (type (x)) 
            selected ['defaults'] = { o : getattr (plot, o) for o in opts if ((o not in selected) and hasattr (plot, o)) } 
key = (keyfn (x) if keyfn else None) 
        return (key, selected) 
traversed = obj.traverse (lookup, specs) 
    options = defaultdict ((lambda : defaultdict (list))) 
    default_opts = defaultdict ((lambda : defaultdict (list))) 
    for (key, opts) in traversed : 
        defaults = opts.pop ('defaults', { 
            
}) 
        for (opt, v) in opts.items () : 
            options [key] [opt].append (v) 
for (opt, v) in defaults.items () : 
            default_opts [key] [opt].append (v) 
for (key, opts) in default_opts.items () : 
        for (opt, v) in opts.items () : 
            if (opt not in options [opt]) : 
                options [key] [opt] = v 
return (options if keyfn else options [None]) 

    
    

    Fix the buggy line: if (opt not in options [opt]) :
assistant
#Here is Python code to fix the buggy line: if (opt not in options [opt]) :
.

if (opt not in options [key]) :