user: I'm deep into this demographic analysis project and I've got a pile of zip codes to work through. Right now, I'm focused on 90210, and I need to match it with its city. Could you provide me with the city name for zip code 90210?

Available functions:
name: retrieve_city_based_on_zipcode
description: Finds the city of a zipcode.
parameters: type: dict
properties: zipcode: type: string
description: The zipcode of the city.
required: zipcode