<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def by_population(self, lower=-1, upper=2 ** 31, zipcode_type=ZipcodeType.Standard, sort_by=SimpleZipcode.population.name, ascending=False, returns=DEFAULT_LIMIT):
 """ Search zipcode information by population range. """

        return self.query(
            population_lower=lower,
            population_upper=upper,
            sort_by=sort_by, zipcode_type=zipcode_type,
            ascending=ascending, returns=returns,
        )