def __init__(self):
        self.children = []
Testing the `difference`, `intersection`, `sym_difference`, and `union` GeoQuerySet methods.
dataset/ETHPy150Open timonwong/OmniMarkupPreviewer/OmniMarkupLib/Renderers/libs/python2/genshi/builder.py/Fragment.__init__--crossover with--dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.5/django/contrib/gis/tests/geoapp/tests.py/GeoQuerySetTest.test_diff_intersection_union