def get_prep_lookup(self, lookup_type, value):
        if lookup_type == 'isnull':
            return value
        return self.get_prep_value(value)
return the underlying data as an ndarray
dataset/ETHPy150Open djangonauts/django-hstore/django_hstore/fields.py/SerializedDictionaryField.get_prep_lookup--crossover with--dataset/ETHPy150Open pydata/pandas/pandas/indexes/base.py/Index.get_values