Writes Header into filename on disk.

        Args:
            filename: Filename and path for file to be written to disk

def write_file(self, filename='HEADER'):
        """
        Writes Header into filename on disk.

        Args:
            filename: Filename and path for file to be written to disk
        """
        with open(filename, "w") as f:
            f.write(str(self) + "\n")