Set format to use in DataframeEditor.

        Args:
            new_format (string): e.g. "%.3f"

def set_dataframe_format(self, new_format):
        """
        Set format to use in DataframeEditor.

        Args:
            new_format (string): e.g. "%.3f"
        """
        self.sig_option_changed.emit('dataframe_format', new_format)
        self.model.dataframe_format = new_format