Writes LammpsData to file.

        Args:
            filename (str): Filename.
            distance (int): No. of significant figures to output for
                box settings (bounds and tilt) and atomic coordinates.
                Default to 6.
            velocity (int): No. of significant figures to output for
                velocities. Default to 8.
            charge (int): No. of significant figures to output for
                charges. Default to 3.

def write_file(self, filename, distance=6, velocity=8, charge=3):
        """
        Writes LammpsData to file.

        Args:
            filename (str): Filename.
            distance (int): No. of significant figures to output for
                box settings (bounds and tilt) and atomic coordinates.
                Default to 6.
            velocity (int): No. of significant figures to output for
                velocities. Default to 8.
            charge (int): No. of significant figures to output for
                charges. Default to 3.

        """
        with open(filename, "w") as f:
            f.write(self.get_string(distance=distance, velocity=velocity,
                                    charge=charge))