Added missing Area import in operation/element.py
@@ -12,7 +12,7 @@ from ..core import (ElementOperation, NdOverlay, Overlay, GridMatrix,
HoloMap, Dataset, Element, Collator)
from ..core.data import ArrayInterface, DictInterface
from ..core.util import find_minmax, group_sanitizer, label_sanitizer, pd
-from ..element.chart import Histogram, Scatter
+from ..element.chart import Histogram, Scatter, Area
from ..element.raster import Raster, Image, RGB, QuadMesh
from ..element.path import Contours, Polygons
from ..element.util import categorical_aggregate2d
