code: def _call(self, x, out=None):
          
          if out is None:
              out = self.range.element()
  
          x_arr = x.asarray()
          ndim = self.domain.ndim
          dx = self.domain.cell_sides
  
          for axis in range(ndim):
              with writable_array(out[axis]) as out_arr:
                  finite_diff(x_arr, axis=axis, dx=dx[axis], method=self.method,
                              pad_mode=self.pad_mode,
                              pad_const=self.pad_const,
                              out=out_arr)
          return out
docs: Calculate the spatial gradient of ``x``.