fix py_reader demo (#16997)

test=develop

paddle/fluid/API.spec

@@ -249,8 +249,8 @@ paddle.fluid.layers.shuffle (ArgSpec(args=['reader', 'buffer_size'], varargs=Non
 paddle.fluid.layers.batch (ArgSpec(args=['reader', 'batch_size'], varargs=None, keywords=None, defaults=None), ('document', 'f563d376d35e1a4c4db100fd11b381a0'))
 paddle.fluid.layers.double_buffer (ArgSpec(args=['reader', 'place', 'name'], varargs=None, keywords=None, defaults=(None, None)), ('document', '07e5b796674796eb1ef3fee9c10d24e3'))
 paddle.fluid.layers.random_data_generator (ArgSpec(args=['low', 'high', 'shapes', 'lod_levels', 'for_parallel'], varargs=None, keywords=None, defaults=(True,)), ('document', '9b7f0f86ec24bbc97643cadcb6499cff'))
-paddle.fluid.layers.py_reader (ArgSpec(args=['capacity', 'shapes', 'dtypes', 'lod_levels', 'name', 'use_double_buffer'], varargs=None, keywords=None, defaults=(None, None, True)), ('document', '4357643685cfd65454ba5a15f0151709'))
-paddle.fluid.layers.create_py_reader_by_data (ArgSpec(args=['capacity', 'feed_list', 'name', 'use_double_buffer'], varargs=None, keywords=None, defaults=(None, True)), ('document', '350f74d93fab9adb2ac4950f1c26416b'))
+paddle.fluid.layers.py_reader (ArgSpec(args=['capacity', 'shapes', 'dtypes', 'lod_levels', 'name', 'use_double_buffer'], varargs=None, keywords=None, defaults=(None, None, True)), ('document', 'c67f756da46159328d23fca29f599d8b'))
+paddle.fluid.layers.create_py_reader_by_data (ArgSpec(args=['capacity', 'feed_list', 'name', 'use_double_buffer'], varargs=None, keywords=None, defaults=(None, True)), ('document', '8acfa165dc4306ac437cc2f10b51b8f5'))
 paddle.fluid.layers.Preprocessor.__init__ (ArgSpec(args=['self', 'reader', 'name'], varargs=None, keywords=None, defaults=(None,)), ('document', '6adf97f83acf6453d4a6a4b1070f3754'))
 paddle.fluid.layers.Preprocessor.block (ArgSpec(args=['self'], varargs=None, keywords=None, defaults=None), ('document', '6adf97f83acf6453d4a6a4b1070f3754'))
 paddle.fluid.layers.Preprocessor.inputs (ArgSpec(args=['self'], varargs=None, keywords=None, defaults=None), ('document', '6adf97f83acf6453d4a6a4b1070f3754'))

python/paddle/fluid/layers/io.py

@@ -684,7 +684,7 @@ def py_reader(capacity,
         >>>                                 shapes=[(-1,3,224,224), (-1,1)],
         >>>                                 dtypes=['float32', 'int64'])
         >>> reader.decorate_paddle_reader(
-        >>>     paddle.reader.shuffle(paddle.batch(mnist.train())
+        >>>     paddle.reader.shuffle(paddle.batch(mnist.train())))
         >>>
         >>> img, label = fluid.layers.read_file(reader)
         >>> loss = network(img, label) # some network definition
@@ -721,7 +721,7 @@ def py_reader(capacity,
         >>>                                       dtypes=['float32', 'int64'],
         >>>                                       name='train_reader')
         >>> train_reader.decorate_paddle_reader(
-        >>>     paddle.reader.shuffle(paddle.batch(mnist.train())
+        >>>     paddle.reader.shuffle(paddle.batch(mnist.train())))
         >>>
         >>> test_reader = fluid.layers.py_reader(capacity=32,
         >>>                                      shapes=[(-1,3,224,224), (-1,1)],
@@ -811,7 +811,7 @@ def create_py_reader_by_data(capacity,
         >>> label = fluid.layers.data(name='label', shape=[1], dtypes='int64')
         >>> reader = fluid.layers.create_py_reader_by_data(capacity=64, feed_list=[image, label])
         >>> reader.decorate_paddle_reader(
-        >>>     paddle.reader.shuffle(paddle.batch(mnist.train())
+        >>>     paddle.reader.shuffle(paddle.batch(mnist.train())))
         >>>
         >>> img, label = fluid.layers.read_file(reader)
         >>> loss = network(img, label) # some network definition