Revert pretrained argument, and remove it's deprecation sign.

mmcls/models/classifiers/image.py

@@ -12,10 +12,13 @@ def __init__(self,
                  backbone,
                  neck=None,
                  head=None,
+                 pretrained=None,
                  train_cfg=None,
                  init_cfg=None):
         super(ImageClassifier, self).__init__(init_cfg)
 
+        if pretrained is not None:
+            self.init_cfg = dict(type='Pretrained', checkpoint=pretrained)
         self.backbone = build_backbone(backbone)
 
         if neck is not None:

tests/test_models/test_classifiers.py

@@ -4,6 +4,7 @@
 from copy import deepcopy
 
 import numpy as np
+import pytest
 import torch
 from mmcv import ConfigDict
 
@@ -84,6 +85,14 @@ def test_image_classifier():
     assert soft_pred.shape == (16, 10)
     torch.testing.assert_allclose(soft_pred, torch.softmax(pred, dim=1))
 
+    # test pretrained
+    with pytest.warns(UserWarning):
+        model_cfg_ = deepcopy(model_cfg)
+        model_cfg_['pretrained'] = 'checkpoint'
+        model = CLASSIFIERS.build(model_cfg_)
+        assert model.init_cfg == dict(
+            type='Pretrained', checkpoint='checkpoint')
+
     # test show_result
     img = np.random.randint(0, 256, (224, 224, 3)).astype(np.uint8)
     result = dict(pred_class='cat', pred_label=0, pred_score=0.9)