code: def is_volume(self):
          
          valid = bool(self.is_watertight and
                       self.is_winding_consistent and
                       np.isfinite(self.center_mass).all() and
                       self.volume > 0.0)
          return valid
docs: Check if a mesh has all the properties required to represent
          a valid volume, rather than just a surface.
  
          These properties include being watertight, having consistent
          winding and outward facing normals.
  
          Returns
          ---------
          valid : bool
            Does the mesh represent a volume