fix typo in wrapper and UT

Author: ChiahsinChu

deepmd/pt/train/wrapper.py

@@ -191,7 +191,7 @@ def forward(
             if self.modifier is not None:
                 modifier_pred = self.modifier(**input_dict)
                 for k, v in modifier_pred.items():
-                    model_pred[k] = model_pred[k] - v
+                    model_pred[k] = model_pred[k] + v
             return model_pred, None, None
         else:
             natoms = atype.shape[-1]

source/tests/pt/test_data_modifier.py

@@ -374,11 +374,11 @@ def test_inference(self):
         model_pred = model.eval(coord, cell, atype)
         modifier_pred = modifier.eval(coord, cell, atype)
         model_pred_ref = model_ref.eval(coord, cell, atype)
-        # expected: output_model - sfactor * output_modifier
+        # expected: output_model = output_model_ref + sfactor * output_modifier
         for ii in range(3):
             np.testing.assert_allclose(
                 model_pred[ii],
-                model_pred_ref[ii] - sfactor * modifier_pred[ii],
+                model_pred_ref[ii] + sfactor * modifier_pred[ii],
                 rtol=1e-5,
                 atol=1e-8,
             )