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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def save_raw(self):
 """ Save the model to a in memory buffer represetation Returns ------- a in memory buffer represetation of the model """

        length = ctypes.c_ulong()
        cptr = ctypes.POINTER(ctypes.c_char)()
        _check_call(_LIB.XGBoosterGetModelRaw(self.handle,
                                              ctypes.byref(length),
                                              ctypes.byref(cptr)))
        return ctypes2buffer(cptr, length.value)