human
Solve the following python programming problem given the following code:
def main_effect(self, reference = None) : 
    "
        Return the 'main effect' columns of a factor, choosing
        an optional reference key.

\tThe reference key can be one of the keys of the Factor,
        or an integer, representing which column to remove.
        It defaults to 0.

        " 
    names = self.names () 
    if (reference is None) : 
        reference = 0 
else : 
        try : 
            reference = self.keys.index (reference) 
except ValueError : 
            reference = int (reference) 
def maineffect_func(value, reference = reference) : 
        rvalue = [] 
        keep = lrange (value.shape [0]) 
        keep.pop (reference) 
        for i in range (len (keep)) : 
            rvalue.append ((value [keep [i]] - value [reference])) 
return np.array (rvalue) 
keep = lrange (len (self.names ())) 
    keep.pop (reference) 
    __names = self.names () 
    _names = [('%s-%s' % (__names [keep [i]], __names [reference])) for i in range (len (keep))] 
    value = Quantitative (_names, func = self, termname = ('%s:maineffect' % self.termname), transform = __names) 
    value.namespace = self.namespace 
    return value 

    
    

    Fix the buggy line: value = Quantitative (_names, func = self, termname = ('%s:maineffect' % self.termname), transform = __names)
assistant
#Here is Python code to fix the buggy line: value = Quantitative (_names, func = self, termname = ('%s:maineffect' % self.

value = Quantitative (_names, func = self, termname = ('%s:maineffect' % self.termname), transform = def maineffect_func()