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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 list_attr(self, recursive=False):
 """Gets all attributes from the symbol. Example ------- {'mood': 'angry'} Returns ------- ret : Dict of str to str A dictionary mapping attribute keys to values. """

        if recursive:
            raise DeprecationWarning("Symbol.list_attr with recursive=True has been deprecated. "
                                     "Please use attr_dict instead.")
        size = mx_uint()
        pairs = ctypes.POINTER(ctypes.c_char_p)()
        f_handle = _LIB.MXSymbolListAttrShallow
        check_call(f_handle(self.handle, ctypes.byref(size), ctypes.byref(pairs)))
        return {py_str(pairs[i * 2]): py_str(pairs[i * 2 + 1]) for i in range(size.value)}