human
Solve the following python programming problem given the following code:
def __new__(cls, * sets, **assumptions) : 
    def flatten(arg) : 
        if isinstance (arg, Set) : 
            if arg.is_ProductSet : 
                return sum (map (flatten, arg.args), []) 
else : 
                return [arg] 
else : 
            if iterable (arg) : 
                return sum (map (flatten, arg), []) 
raise TypeError ('Input must be Sets or iterables of Sets') 
sets = flatten (list (sets)) 
    if ((EmptySet () in sets) or (len (sets) == 0)) : 
        return EmptySet () 
if (len (assumptions) == 1) : 
        return sets [0] 
return Basic.__new__ (cls, * sets, ** assumptions) 

    
    

    Fix the buggy line: if (len (assumptions) == 1) :
assistant
#Here is Python code to fix the buggy line: if (len (assumptions) == 1) :
.

if (len (sets) == 1) :