本案例将一个自己圈定的shp文件导出来：
这个函数是要求你得把自己圈定的点线面，转化为矢量集合
ee.FeatureCollection(args, column)
FeatureCollections can be constructed from the following arguments:
A string: assumed to be the name of a collection.
A single geometry.
A single feature.
A list of features.
A GeoJSON FeatureCollection
A computed object: reinterpreted as a collection.
Arguments:
args (ComputedObject|Feature|FeatureCollection|Geometry|List<Object>|Number|String):
The constructor arguments.
column (String, optional):
The name of the geometry column to use. Only useful when working with a named collection.
Returns: FeatureCollection
Export.table.toDrive(collection, description, folder, fileNamePrefix, fileFormat, selectors, maxVertices)
创建一个批处理任务，将FeatureCollection作
