WeChat.Material.get_media

You're seeing just the function get_media, go back to WeChat.Material module for more information.
Link to this function

get_media(client, media_id)

Specs

get_media(WeChat.client(), media_id()) :: WeChat.response()

获取临时素材 - 官方文档

公众号可以使用本接口获取临时素材(即下载临时的多媒体文件)。