some tensorflow function not work

[zhulunwu]

Environment: win 10 , julia 1.5.1 , tensorflow 2.3
following code not work

using PyCall
tf=pyimport("tensorflow")
f(x,y)=x+y
tf.function(f)

ERROR: PyError ($(Expr(:escape, :(ccall(#= C:\Program Files\Julia\local\share\julia\packages\PyCall\BcTLp\src\pyfncall.jl:43 =# @pysym(:PyObject_Call), PyPtr, (PyPtr, PyPtr, PyPtr), o, pyargsptr, kw))))) <class 'TypeError'>
TypeError('unsupported callable')
File "C:\Program Files\Julia\local\Python38\lib\site-packages\tensorflow\python\eager\def_function.py", line 1443, in function
return decorated(func)
File "C:\Program Files\Julia\local\Python38\lib\site-packages\tensorflow\python\eager\def_function.py", line 1431, in decorated
decorator_func=Function(
File "C:\Program Files\Julia\local\Python38\lib\site-packages\tensorflow\python\eager\def_function.py", line 521, in init
self._function_spec = function_lib.FunctionSpec.from_function_and_signature(
File "C:\Program Files\Julia\local\Python38\lib\site-packages\tensorflow\python\eager\function.py", line 2313, in from_function_and_signature
fullargspec = tf_inspect.getfullargspec(python_function)
File "C:\Program Files\Julia\local\Python38\lib\site-packages\tensorflow\python\util\tf_inspect.py", line 257, in getfullargspec
return _getfullargspec(target)
File "C:\Program Files\Julia\local\Python38\lib\inspect.py", line 1132, in getfullargspec
raise TypeError('unsupported callable') from ex

Stacktrace:
[1] pyerr_check at C:\Program Files\Julia\local\share\julia\packages\PyCall\BcTLp\src\exception.jl:62 [inlined]
[2] pyerr_check at C:\Program Files\Julia\local\share\julia\packages\PyCall\BcTLp\src\exception.jl:66 [inlined]
[3] _handle_error(::String) at C:\Program Files\Julia\local\share\julia\packages\PyCall\BcTLp\src\exception.jl:83