boost python的指针参数

使以指针为参数的函数与boostpython一起工作的最佳方法是什么?

void Tesuto::testp(std::string* s)
{
    if (!s)
        cout << " NULL s" << endl;
    else
        cout << s << endl;
}

>>> t.testp(None)
 NULL s
>>>       
>>> s='test'
>>> t.testp(s)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
Boost.Python.ArgumentError: Python argument types in
    Tesuto.testp(Tesuto, str)
did not match C++ signature:
    testp(Tesuto {lvalue}, std::string*)
>>>