def add_pop_key_list(self, key):
        if key not in self.pop_key_list:
            self.pop_key_list.append(key)
Equivalence is equivalent types (????)
dataset/ETHPy150Open modflowpy/flopy/flopy/mbase.py/BaseModel.add_pop_key_list--crossover with--dataset/ETHPy150Open cidles/graf-python/src/graf/annotations.py/FeatureStructure.__eq__