code: def add_path(self, w, h):
          
          custGeom = self.spPr.custGeom
          if custGeom is None:
              raise ValueError('shape must be freeform')
          pathLst = custGeom.get_or_add_pathLst()
          return pathLst.add_path(w=w, h=h)
docs: Reference to `a:custGeom` descendant or |None| if not present.