add a argument for softshrink python api (#19396)

* test=develop add a argument for softshrink python api

* test=develop fix doc format 

test=develop fix doc format

* test=develop fix API.spec

test=develop fix API.spec

paddle/fluid/API.spec

@@ -372,7 +372,6 @@ paddle.fluid.layers.exp (ArgSpec(args=['x', 'name'], varargs=None, keywords=None
 paddle.fluid.layers.tanh (ArgSpec(args=['x', 'name'], varargs=None, keywords=None, defaults=(None,)), ('document', 'f820eeaf81dfbdd1c360122cd5795cc8'))
 paddle.fluid.layers.atan (ArgSpec(args=['x', 'name'], varargs=None, keywords=None, defaults=(None,)), ('document', '2dde114018cbcaff9b24c566bf6704a5'))
 paddle.fluid.layers.tanh_shrink (ArgSpec(args=['x', 'name'], varargs=None, keywords=None, defaults=(None,)), ('document', '63d198e36e1d85dcfb454c1a3cb3b38e'))
-paddle.fluid.layers.softshrink (ArgSpec(args=['x', 'name'], varargs=None, keywords=None, defaults=(None,)), ('document', '4f53a5e7f50c55ea516375ef8f46316b'))
 paddle.fluid.layers.sqrt (ArgSpec(args=['x', 'name'], varargs=None, keywords=None, defaults=(None,)), ('document', '893ec81a025f3c82f1c8fca6aa84d39f'))
 paddle.fluid.layers.rsqrt (ArgSpec(args=['x', 'name'], varargs=None, keywords=None, defaults=(None,)), ('document', 'c629f5163fa04f80abb3d0240c462fa6'))
 paddle.fluid.layers.abs (ArgSpec(args=['x', 'name'], varargs=None, keywords=None, defaults=(None,)), ('document', 'f6d5642f52e357f3cec89cc9c15dc66c'))
@@ -388,6 +387,7 @@ paddle.fluid.layers.square (ArgSpec(args=['x', 'name'], varargs=None, keywords=N
 paddle.fluid.layers.softplus (ArgSpec(args=['x', 'name'], varargs=None, keywords=None, defaults=(None,)), ('document', 'be4533a4cd97c84424512dca76142083'))
 paddle.fluid.layers.softsign (ArgSpec(args=['x', 'name'], varargs=None, keywords=None, defaults=(None,)), ('document', '410f27a44b7365cc60d5d5ff5a53407e'))
 paddle.fluid.layers.uniform_random (ArgSpec(args=['shape', 'dtype', 'min', 'max', 'seed'], varargs=None, keywords=None, defaults=('float32', -1.0, 1.0, 0)), ('document', '6de6775d9e9ed885056e764982130cfd'))
+paddle.fluid.layers.softshrink (ArgSpec(args=['x', 'alpha'], varargs=None, keywords=None, defaults=(None,)), ('document', '958c7bfdfb0b5e92af6ca4a90d24e5ef'))
 paddle.fluid.layers.hard_shrink (ArgSpec(args=['x', 'threshold'], varargs=None, keywords=None, defaults=(None,)), ('document', '386a4103d2884b2f1312ebc1e8ee6486'))
 paddle.fluid.layers.cumsum (ArgSpec(args=['x', 'axis', 'exclusive', 'reverse'], varargs=None, keywords=None, defaults=(None, None, None)), ('document', '5ab9d5721a6734fe127069e4314e1309'))
 paddle.fluid.layers.thresholded_relu (ArgSpec(args=['x', 'threshold'], varargs=None, keywords=None, defaults=(None,)), ('document', '9a0464425426a9b9c1b7500ede2836c1'))

python/paddle/fluid/layers/ops.py

@@ -25,7 +25,6 @@ __activations_noattr__ = [
     'tanh',
     'atan',
     'tanh_shrink',
-    'softshrink',
     'sqrt',
     'rsqrt',
     'abs',
@@ -97,6 +96,49 @@ def uniform_random(shape, dtype='float32', min=-1.0, max=1.0, seed=0):
     return _uniform_random_(**kwargs)
 
 
+__all__ += ['softshrink']
+
+_softshrink_ = generate_layer_fn('softshrink')
+
+
+def softshrink(x, alpha=None):
+    locals_var = locals().copy()
+    kwargs = dict()
+    for name, val in locals_var.items():
+        if val is not None:
+            if name == 'alpha':
+                kwargs['lambda'] = val
+            else:
+                kwargs[name] = val
+    return _softshrink_(**kwargs)
+
+
+softshrink.__doc__ = """
+:strong:`Softshrink Activation Operator`
+
+..  math::
+    out = \begin{cases}
+            x - \alpha, \text{if } x > \alpha \\
+            x + \alpha, \text{if } x < -\alpha \\
+            0,  \text{otherwise}
+            \end{cases}
+
+
+Args:
+    x: Input of Softshrink operator
+    alpha (FLOAT): non-negative offset
+    
+Returns:
+    Output of Softshrink operator
+
+Examples:
+    .. code-block:: python
+    
+        import paddle.fluid as fluid
+        data = fluid.layers.data(name="input", shape=[784])
+        result = fluid.layers.softshrink(x=data, alpha=0.3)
+"""
+
 __all__ += ['hard_shrink']
 
 _hard_shrink_ = generate_layer_fn('hard_shrink')

python/paddle/fluid/tests/unittests/test_layers.py

@@ -1813,7 +1813,7 @@ class TestBook(LayerTest):
         with program_guard(fluid.default_main_program(),
                            fluid.default_startup_program()):
             input = self._get_data(name="input", shape=[16], dtype="float32")
-            out = layers.softshrink(input, name='softshrink')
+            out = layers.softshrink(input, alpha=0.3)
             return (out)
 
     def make_iou_similarity(self):