typo of unstack layer

Author: zsdonghao

tensorlayer/layers.py

@@ -6305,7 +6305,7 @@ def UnStackLayer(
         axis = 0,
         name ='unstack',):
     """
-    The `UnStackLayer` is layer for unstacking the given dimension of a rank-R tensor into rank-(R-1) tensors., see `tf.unstack() <https://www.tensorflow.org/api_docs/python/tf/unstack>`_.
+    The :class:`UnStackLayer` is layer for unstacking the given dimension of a rank-R tensor into rank-(R-1) tensors., see `tf.unstack() <https://www.tensorflow.org/api_docs/python/tf/unstack>`_.
 
     Parameters
     ----------