human
Solve the following python programming problem given the following code:
def flatten_opts(opts) : 
    r = [] 
    def to_opt(x) : 
        return '--{0}'.format (x) 
for (k, v) in opts.items () : 
        if (v is None) : 
            r.append (to_opt (k)) 
else : 
            if (type (to_opt) is list) : 
                for n in v : 
                    r.extend ([to_opt (k), str (n)]) 
else : 
                r.extend ([to_opt (k), str (v)]) 
return r 

    
    

    Fix the buggy line: if (type (to_opt) is list) :
assistant
#Here is Python program to fix the buggy line: if (type (to_opt) is list) :
.

if (type (v) is list) :