Geofence mechanism is updated according to V2.1.0.

The process of setting the geofence in V1 was different than V2, so this change updated the geofence process according to the need of V2.
Geofence class is changed.

examples/geofence.py

@@ -2,14 +2,18 @@
 
 import asyncio
 from mavsdk import System
-from mavsdk.geofence import Point, Polygon
+from mavsdk.geofence import Point, Polygon, FenceType, GeofenceData, Circle
 
 """
 This example shows how to use the geofence plugin.
 
 Note: The behavior when your vehicle hits the geofence is NOT configured
 in this example.
 
+FenceType:
+    INCLUSION: The vehicle will not go outside the fence area.
+    EXCLUSION: The vehicle will not come inside the fence area.
+
 """
 
 
@@ -43,11 +47,19 @@ async def run():
     p4 = Point(latitude - 0.0001, longitude + 0.0001)
 
     # Create a polygon object using your points
-    polygon = Polygon([p1, p2, p3, p4], Polygon.FenceType.INCLUSION)
+    polygon = Polygon([p1, p2, p3, p4], FenceType.INCLUSION)
+
+    # circle = Circle(p1, 10.0, FenceType.INCLUSION)
+
+    # Sending the circle object is necessary in the geofence data, 
+    # so if you don't want to set the circular geofence, send it like this.
+    circle = Circle(Point(0,0), 0, FenceType.INCLUSION)
+
+    geofenceData = GeofenceData([polygon], [circle])
 
     # Upload the geofence to your vehicle
     print("Uploading geofence...")
-    await drone.geofence.upload_geofence([polygon])
+    await drone.geofence.upload_geofence(geofenceData)
 
     print("Geofence uploaded!")