Save DMatrix to an XGBoost buffer.  Saved binary can be later loaded
        by providing the path to :py:func:`xgboost.DMatrix` as input.

        Parameters
        ----------
        fname : string
            Name of the output buffer file.
        silent : bool (optional; default: True)
            If set, the output is suppressed.

def save_binary(self, fname, silent=True):
        """Save DMatrix to an XGBoost buffer.  Saved binary can be later loaded
        by providing the path to :py:func:`xgboost.DMatrix` as input.

        Parameters
        ----------
        fname : string
            Name of the output buffer file.
        silent : bool (optional; default: True)
            If set, the output is suppressed.
        """
        _check_call(_LIB.XGDMatrixSaveBinary(self.handle,
                                             c_str(fname),
                                             ctypes.c_int(silent)))