Update sequence_mask related code (#41393)

python/paddle/fluid/layers/sequence_lod.py

@@ -1382,10 +1382,9 @@ def sequence_mask(x, maxlen=None, dtype='int64', name=None):
 
     """
 
-    if _non_static_mode():
+    if in_dygraph_mode():
         if not isinstance(dtype, core.VarDesc.VarType):
             dtype = convert_np_dtype_to_dtype_(dtype)
-        if in_dygraph_mode():
         if maxlen is not None:
             if isinstance(maxlen, core.eager.Tensor):
                 attrs = ('out_dtype', dtype)

python/paddle/fluid/tests/unittests/test_rnn_decode_api.py

@@ -716,7 +716,6 @@ class TestBeamSearch(ModuleApiTest):
     def func_check_output(self):
         self.setUp()
         self.make_inputs()
-        self.make_inputs()
         self.check_output()
 
     def test_check_output(self):