Generate docs for Fluid API (#6215)

* add doc config for fluid

* fix typo

* follow comments

Author: QiJune

doc/api/index_en.rst

@@ -7,3 +7,4 @@ API
     v2/model_configs.rst
     v2/data.rst
     v2/run_logic.rst
+    v2/fluid.rst

doc/api/v2/fluid.rst

@@ -0,0 +1,18 @@
+======================
+Fluid
+======================
+
+..  toctree::
+    :maxdepth: 1
+
+    fluid/layers.rst
+    fluid/data_feeder.rst
+    fluid/executor.rst
+    fluid/initializer.rst
+    fluid/evaluator.rst
+    fluid/nets.rst
+    fluid/optimizer.rst
+    fluid/param_attr.rst
+    fluid/profiler.rst
+    fluid/regularizer.rst
+

doc/api/v2/fluid/data_feeder.rst

@@ -0,0 +1,9 @@
+===========
+DataFeeder
+===========
+
+DataFeeder
+-----------
+..  automodule:: paddle.v2.fluid.data_feeder
+    :members: DataFeeder
+    :noindex:

doc/api/v2/fluid/evaluator.rst

@@ -0,0 +1,9 @@
+===========
+Evaluator
+===========
+
+Evaluator
+-----------
+..  automodule:: paddle.v2.fluid.evaluator
+    :members: Evaluator
+    :noindex:

doc/api/v2/fluid/executor.rst

@@ -0,0 +1,9 @@
+===========
+Executor
+===========
+
+Executor
+-----------
+..  automodule:: paddle.v2.fluid.executor
+    :members: Executor
+    :noindex:

doc/api/v2/fluid/initializer.rst

@@ -0,0 +1,50 @@
+===========
+Initializer
+===========
+
+
+
+Initializer
+-----------
+..  automodule:: paddle.v2.fluid.initializer
+    :members: Initializer
+    :noindex:
+
+
+
+ConstantInitializer
+-------------------
+..  automodule:: paddle.v2.fluid.initializer
+    :members: ConstantInitializer
+    :noindex:
+
+
+
+UniformInitializer
+------------------
+..  automodule:: paddle.v2.fluid.initializer
+    :members: UniformInitializer
+    :noindex:
+
+
+
+NormalInitializer
+-----------------
+..  automodule:: paddle.v2.fluid.initializer
+    :members: NormalInitializer
+    :noindex:
+
+
+XavierInitializer
+-----------------
+..  automodule:: paddle.v2.fluid.initializer
+    :members: XavierInitializer
+    :noindex:
+
+
+MSRAInitializer
+---------------
+..  automodule:: paddle.v2.fluid.initializer
+    :members: MSRAInitializer
+    :noindex:
+