In chapter 8, we designed a GraphQL API for the products service, and we produced a specification detailing the requirements for the products API. In this chapter, we implement the API according to the specification. To build the API, we’ll use the Ariadne framework, which is one of the most popular GraphQL libraries in the Python ecosystem. Ariadne allows us to leverage the benefits of documentation-driven development by automatically loading data validation models from the specification. We’ll learn to create resolvers, which are Python functions that implement the logic of a query or mutation. We’ll also learn to handle queries that return multiple types. After reading this chapter, you’ll have all the tools you need to start developing your own GraphQL APIs!