What is the transform attribute in the axios configuration?

Could you give me a general idea of its usage? I can't find the relevant description in github's document.I found it in a vue template of github(vue-vben-admin, https://github.com/vbenjs/vue-vben-admin). Its directory is src/http/axios/index.ts. It returns a VAxios call of constructor in a function called createAxios, and a configuration object is passed in. The transform attribute is in this configuration object.