A Lazy ModelChoiceField implementation

class LazyModelChoiceField(forms.ChoiceField):
    '''
    A Lazy ModelChoiceField, similar to LazyChoiceField
    not overriding ModelChoiceField, since we need to convert the queryset into a tuple to sort it
    This allows for dynamic choices generation every time an instance of a Form is created.
    '''
    def __init__(self, *args, **kwargs):
	self.sort_by = kwargs.pop('sort_by', ())
	self.queryset = kwargs.pop('queryset', ())
	self.empty_label = kwargs.pop('empty_label', ())
        super(LazyModelChoiceField, self).__init__(*args, **kwargs)
        
    def __deepcopy__(self, memo):
        result = super(LazyModelChoiceField, self).__deepcopy__(memo)
        # requires of ugettext_lazy as _
        result.choices = ()
        for entry in self.queryset():
	    result.choices.append((entry.id, _(entry.__getattribute__(self.sort_by))))
	result.choices.sort(lambda x, y: cmp(x[1], y[1]))
        result.choices.insert(0, (0, self.empty_label))
	return result