Gets all attributes from the symbol.

        Example
        -------
        >>> data = mx.sym.Variable('data', attr={'mood': 'angry'})
        >>> data.list_attr()
        {'mood': 'angry'}

        Returns
        -------
        ret : Dict of str to str
            A dictionary mapping attribute keys to values.

def list_attr(self, recursive=False):
        """Gets all attributes from the symbol.

        Example
        -------
        >>> data = mx.sym.Variable('data', attr={'mood': 'angry'})
        >>> data.list_attr()
        {'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)}