def __init__(self, children=None, connector=None, negated=False):
        if children is not None and len(children) > 1 and connector is None:
            raise TypeError('You have to specify a connector.')
        super(ExpressionNode, self).__init__(children, connector, negated)
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.5/django/db/models/expressions.py/ExpressionNode.__init__/original