def _get_rel_of_type(self, reltype):
        matching = [rel for rel in self.values() if rel.reltype == reltype]
        if len(matching) == 0:
            tmpl = "no relationship of type '%s' in collection"
            raise KeyError(tmpl % reltype)
        if len(matching) > 1:
            tmpl = "multiple relationships of type '%s' in collection"
            raise ValueError(tmpl % reltype)
        return matching[0]
Test if Numeric/VTK array conversion works.
dataset/ETHPy150Open scanny/python-pptx/pptx/opc/package.py/RelationshipCollection._get_rel_of_type--crossover with--dataset/ETHPy150Open enthought/mayavi/tvtk/tests/test_tvtk.py/TestTVTK.test_array_conversion