@property
    def type(self):
        if self._type is None and len(self):
            self._type = self.values()[0].__class__
        return self._type
when a macro tag uses a template variable to
dataset/ETHPy150Open ioam/holoviews/holoviews/core/ndmapping.py/UniformNdMapping.type--crossover with--dataset/ETHPy150Open nalourie/django-macros/build/lib/macros/tests.py/MacrosTests.test_default_template_variables_set_at_definition