optimize code

test=develop

python/paddle/fluid/transpiler/details/distribute_lookuptable_utils.py

@@ -16,11 +16,12 @@ LOOKUP_TABLE_TYPE = "lookup_table"
 
 
 def find_distributed_lookup_table(program):
-    # process lookup_table_op
-    # 1. check all lookup_table_op is distributed
-    # 2. check all lookup_table_op share the same table.
-    distributed_lookup_table_ops = []
-    # support only one distributed_lookup_table now
+    """
+    Find distribute lookup table in program.
+    We only support one distribute table now.
+    :param program:
+    :return: table_name or None
+    """
     table_name = None
 
     for op in program.global_block().ops:
@@ -31,7 +32,6 @@ def find_distributed_lookup_table(program):
                 if table_name != op.input("W")[0]:
                     raise RuntimeError("all distributed lookup_table_ops"
                                        " should have only one table")
-                distributed_lookup_table_ops.append(op)
             else:
                 if table_name is not None:
                     assert op.input("W")[0] != table_name