创建一个新的要素图层
1.概念
1）developer dashboard：The developer dashboard is the ArcGIS Developers administration website used to manage API keys, monitor service usage, create and manage layers, API downloads, applications, and manage an ArcGIS account.（开发者仪表板是ArcGIS开发者管理网站，用于管理API密钥，监控服务使用，创建和管理层，API下载，应用程序，以及管理ArcGIS帐户。）
2） ArcGIS Online ：ArcGIS Online is a cloud-based portal that connects to the ArcGIS Platform to provide secure mapping, analytics, and data storage. An ArcGIS account is required.