fix api doc

test=develop

python/paddle/fluid/layers/nn.py

@@ -5935,13 +5935,10 @@ def reshape(x, shape, actual_shape=None, act=None, inplace=False, name=None):
                                 than :attr:`shape`.
         act (str): The non-linear activation to be applied to the reshaped tensor
                    variable.
-        inplace(bool): Must use :attr:`False` if :attr:`x` is used in multiple
-                       operators. If this flag is set :attr:`True`, reuse input
-                       :attr:`x` to reshape, which will change the shape of
-                       tensor variable :attr:`x` and might cause errors when
-                       :attr:`x` is used in multiple operators. If :attr:`False`,
-                       preserve the shape :attr:`x` and create a new output tensor
-                       variable whose data is copied from input x but reshaped.
+        inplace(bool): If ``inplace`` is `True`, the input and output of ``layers.reshape``
+                       are the same variable, otherwise, the input and output of
+                       ``layers.reshape`` are different variables. Note that if :attr:`x`
+                       is more than one layers' input, ``inplace`` must be :attr:`False`.
         name (str): The name of this layer. It is optional.
 
     Returns:
@@ -8334,6 +8331,44 @@ def stack(x, axis=0):
     If :code:`axis` < 0, it would be replaced with :code:`axis+rank(x[0])+1`.
     If :code:`axis` is None, it would be replaced with 0.
 
+    .. code-block:: text
+
+        Case 1:
+          Input:
+            x[0].data = [ [1.0 , 2.0 ] ]
+            x[0].dims = [1, 2]
+            x[1].data = [ [3.0 , 4.0 ] ]
+            x[1].dims = [1, 2]
+            x[2].data = [ [5.0 , 6.0 ] ]
+            x[2].dims = [1, 2]
+
+          Attrs:
+            axis = 0
+
+          Output:
+            Out.data =[ [ [1.0, 2.0] ],
+                        [ [3.0, 4.0] ],
+                        [ [5.0, 6.0] ] ]
+            Out.dims = [3, 1, 2]
+
+        Case 2:
+          Given
+            x[0].data = [ [1.0 , 2.0 ] ]
+            x[0].dims = [1, 2]
+            x[1].data = [ [3.0 , 4.0 ] ]
+            x[1].dims = [1, 2]
+            x[2].data = [ [5.0 , 6.0 ] ]
+            x[2].dims = [1, 2]
+
+          Attrs:
+            axis = 1 or axis = -2
+
+          Output:
+            Out.data =[ [ [1.0, 2.0]
+                          [3.0, 4.0]
+                          [5.0, 6.0] ] ]
+            Out.dims = [1, 3, 2]
+
     Args:
         x (Variable|list(Variable)|tuple(Variable)): Input variables.
         axis (int|None): The axis along which all inputs are stacked.

python/paddle/fluid/layers/tensor.py

@@ -567,7 +567,7 @@ def ones(shape, dtype, force_cpu=False):
     It also sets *stop_gradient* to True.
 
     Args:
-        shape(tuple|list|None): Shape of output tensor
+        shape(tuple|list): Shape of output tensor
         dtype(np.dtype|core.VarDesc.VarType|str): Data type of output tensor
 
     Returns:
@@ -578,6 +578,10 @@ def ones(shape, dtype, force_cpu=False):
 
           data = fluid.layers.ones(shape=[1], dtype='int64')
     """
+    assert isinstance(shape, list) or isinstance(
+        shape, tuple), "The shape's type should be list or tuple."
+    assert reduce(lambda x, y: x * y,
+                  shape) > 0, "The shape is invalid: %s." % (str(shape))
     return fill_constant(value=1.0, **locals())