!6192 Improve the functions of class SequentialCell and add examples

Merge pull request !6192 from lijiaqi/sequentialcell

mindspore/nn/layer/container.py

@@ -146,9 +146,20 @@ class SequentialCell(Cell):
             cell.set_grad(flag)
 
     def append(self, cell):
-        """Appends a given cell to the end of the list."""
+        """Appends a given cell to the end of the list.
+
+        Examples:
+        >>> conv = nn.Conv2d(3, 2, 3, pad_mode='valid')
+        >>> bn = nn.BatchNorm2d(2)
+        >>> relu = nn.ReLU()
+        >>> seq = nn.SequentialCell([conv, bn])
+        >>> seq.append(relu)
+        >>> x = Tensor(np.random.random((1, 3, 4, 4)), dtype=mindspore.float32)
+        >>> seq(x)
+        """
         if _valid_cell(cell):
             self._cells[str(len(self))] = cell
+        self.cell_list = list(self._cells.values())
         return self
 
     def construct(self, input_data):

tests/ut/python/nn/test_container.py

@@ -84,6 +84,20 @@ class TestSequentialCell():
         del m[:]
         assert type(m).__name__ == 'SequentialCell'
 
+    def test_sequentialcell_append(self):
+        input_np = np.ones((1, 3)).astype(np.float32)
+        input_me = Tensor(input_np)
+        relu = nn.ReLU()
+        tanh = nn.Tanh()
+        seq = nn.SequentialCell([relu])
+        seq.append(tanh)
+        out_me = seq(input_me)
+
+        seq1 = nn.SequentialCell([relu, tanh])
+        out = seq1(input_me)
+
+        assert out[0][0] == out_me[0][0]
+
 
 class TestCellList():
     """ TestCellList """