code: def invert(self):
          
          with self._cache:
              if 'face_normals' in self._cache:
                  self.face_normals *= -1.0
              if 'vertex_normals' in self._cache:
                  self.vertex_normals *= -1.0
              self.faces = np.fliplr(self.faces)
          # save our normals
          self._cache.clear(exclude=['face_normals',
                                     'vertex_normals'])
docs: Invert the mesh in- place by reversing the winding of every
          face and negating normals without dumping the cache.
  
          Alters
          ---------
          self.faces :          columns reversed
          self.face_normals :   negated if defined
          self.vertex_normals : negated if defined