[Doc] Hotfix on docstring of set_batch_num_edges (#2498)

docs/source/api/python/dgl.DGLGraph.rst

@@ -164,10 +164,10 @@ Methods for performing message passing, applying functions on node/edge features
     DGLGraph.filter_nodes
     DGLGraph.filter_edges
 
-Querying batch summary
----------------------------------
+Querying and manipulating batch information
+----------------------------------------------
 
-Methods for getting the batching information if the current graph is a batched
+Methods for getting/setting the batching information if the current graph is a batched
 graph generated from :func:`dgl.batch`. They are also widely used in the
 :ref:`api-batch`.
 
@@ -177,6 +177,9 @@ graph generated from :func:`dgl.batch`. They are also widely used in the
     DGLGraph.batch_size
     DGLGraph.batch_num_nodes
     DGLGraph.batch_num_edges
+    DGLGraph.set_batch_num_nodes
+    DGLGraph.set_batch_num_edges
+
 
 Mutating topology
 -----------------

docs/source/api/python/dgl.rst

@@ -86,8 +86,6 @@ operators for computing graph-level representation for both single and batched g
 
     batch
     unbatch
-    set_batch_num_nodes
-    set_batch_num_edges
     readout_nodes
     readout_edges
     sum_nodes

python/dgl/heterograph.py

@@ -1419,7 +1419,7 @@ class DGLHeteroGraph(object):
 
         Notes
         -----
-        This API is always used together with ``set_batch_num_edges`` to specify batching
+        This API is always used together with ``set_batch_num_nodes`` to specify batching
         information of a graph, it also do not check the correspondance between the graph structure
         and batching information and user must guarantee there will be no cross-graph edges in the
         batch.