def merge(self, other):
        for key, value in other.items():
            if key not in self:
                self[key] = value
Test implicit merging of two cols raises.
dataset/ETHPy150Open duerrp/pyexperiment/pyexperiment/utils/HierarchicalMapping.py/HierarchicalMapping.merge--crossover with--dataset/ETHPy150Open zzzeek/sqlalchemy/test/orm/test_mapper.py/MapperTest.test_mapping_to_join_raises