code: def _call(self, func, out=None, **kwargs):
          
          mesh = self.grid.meshgrid
          if out is None:
              out = func(mesh, **kwargs)
          else:
              with writable_array(out) as out_arr:
                  func(mesh, out=out_arr, **kwargs)
          return out
docs: Return ``self(func[, out, **kwargs])``.