class_docstr: Creates ShapelyAnnotation (as shapely MultiPolygon).
  Can convert this instance annotation to various formats.
code: def area(self):
      return int(self.__area)
  
imports: from typing import List
  from shapely.geometry import CAP_STYLE, JOIN_STYLE, MultiPolygon, Polygon, box
label_desc: Use image node_id 5 for calling the ShapelyAnnotation obj's underlying member method code with example usage: obj.area() and returns: int