fix sequential (#10554)

python/mxnet/gluon/nn/basic_layers.py

@@ -62,7 +62,7 @@ def __repr__(self):
                         modstr=modstr)
 
     def __getitem__(self, key):
-        return self._children[str(key)]
+        return list(self._children.values())[key]
 
     def __len__(self):
         return len(self._children)
@@ -119,7 +119,7 @@ def __repr__(self):
                         modstr=modstr)
 
     def __getitem__(self, key):
-        return self._children[str(key)]
+        return list(self._children.values())[key]
 
     def __len__(self):
         return len(self._children)

tests/python/unittest/test_gluon.py

@@ -609,6 +609,23 @@ def __init__(self, **kwargs):
         model.collect_params()
         assert len(w) == 0
 
+def check_sequential(net):
+    dense1 = gluon.nn.Dense(10)
+    net.add(dense1)
+    dense2 = gluon.nn.Dense(10)
+    net.add(dense2)
+    dense3 = gluon.nn.Dense(10)
+    net.add(dense3)
+
+    assert net[1] is dense2
+    assert net[-1] is dense3
+    slc = net[1:3]
+    assert len(slc) == 2 and slc[0] is dense2 and slc[1] is dense3
+
+@with_seed()
+def test_sequential():
+    check_sequential(gluon.nn.Sequential())
+    check_sequential(gluon.nn.HybridSequential())
 
 @with_seed()
 def test_sequential_warning():