Fix get_py_obj_dtype() for mindspore type

Return mstype.type_type if input is mindspore type object,
for example:
```
get_py_obj_dtype(mstype.float32) ---> mstype.type_type
```

mindspore/common/dtype.py

@@ -178,12 +178,18 @@ def get_py_obj_dtype(obj):
         Type of MindSpore type.
     """
     # Tensor
-    if hasattr(obj, 'dtype') and isinstance(obj.dtype, typing.Type):
+    if hasattr(obj, 'shape') and hasattr(obj, 'dtype') and isinstance(obj.dtype, typing.Type):
         return tensor_type(obj.dtype)
+    # Primitive or Cell
     if hasattr(obj, '__primitive_flag__') or hasattr(obj, 'construct'):
         return function
-    if isinstance(obj, (typing.Type, type)):
+    # mindspore type
+    if isinstance(obj, typing.Type):
+        return type_type
+    # python type
+    if isinstance(obj, type):
         return pytype_to_dtype(obj)
+    # others
     return pytype_to_dtype(type(obj))
 
 

tests/ut/python/pynative_mode/ops/test_grad.py

@@ -19,7 +19,6 @@ import mindspore as ms
 import mindspore.ops.operations as P
 from mindspore import Tensor, context
 from mindspore.common.api import ms_function
-from mindspore.common.dtype import get_py_obj_dtype
 from mindspore.ops import composite as C
 from mindspore.ops import functional as F
 from ...ut_filter import non_graph_engine
@@ -90,7 +89,7 @@ def test_cast_grad():
 def test_scalar_cast_grad():
     """ test_scalar_cast_grad """
     input_x = 255.5
-    input_t = get_py_obj_dtype(ms.int8)
+    input_t = ms.int8
 
     def fx_cast(x):
         output = F.scalar_cast(x, input_t)

tests/ut/python/pynative_mode/test_staging.py

@@ -23,7 +23,6 @@ from mindspore import context
 from mindspore.common import MetaTensor
 from mindspore.common import dtype
 from mindspore.common.api import ms_function
-from mindspore.common.dtype import get_py_obj_dtype
 from mindspore.ops import functional as F
 from mindspore.ops import operations as P
 from ..ut_filter import non_graph_engine
@@ -185,7 +184,7 @@ def test_input_signature():
 def test_scalar_cast():
     """ test_scalar_cast """
     input_x = 8.5
-    input_t = get_py_obj_dtype(ms.int64)
+    input_t = ms.int64
 
     @ms_function
     def fn_cast(x, t):