How to use the f90nml.write function in f90nml

def assert_write_file(self, nml, target_fname, sort=False):
        tmp_fname = 'tmp.nml'
        with open(tmp_fname, 'w') as tmp_file:
            f90nml.write(nml, tmp_file, sort=sort)
            self.assertFalse(tmp_file.closed)
        try:
            self.assert_file_equal(tmp_fname, target_fname)
        finally:
            os.remove(tmp_fname)

def assert_write_path(self, nml, target_fname, sort=False):
        tmp_fname = 'tmp.nml'
        f90nml.write(nml, tmp_fname, sort=sort)
        try:
            self.assert_file_equal(tmp_fname, target_fname)
        finally:
            os.remove(tmp_fname)

def init_config(self):
        """Patch input.nml as a new or restart run."""

        input_fpath = os.path.join(self.work_path, 'input.nml')

        input_nml = f90nml.read(input_fpath)

        input_type = 'n' if self.expt.counter == 0 else 'r'
        input_nml['GOLD_input_nml']['input_filename'] = input_type

        f90nml.write(input_nml, input_fpath, force=True)

# Write to output
        if not args.patch:
            if output_fmt in ('json', 'yaml'):
                if output_fmt == 'json':
                    input_data = input_data.todict(complex_tuple=True)
                    json.dump(input_data, output_file,
                              indent=4, separators=(',', ': '))
                    output_file.write('\n')

                elif output_fmt == 'yaml':
                    input_data = input_data.todict(complex_tuple=True)
                    yaml.dump(input_data, output_file,
                              default_flow_style=False)
            else:
                # Default to namelist output
                f90nml.write(input_data, output_file)

    # Cleanup
    if output_file != sys.stdout:
        output_file.close()

def init_config(self):
        """Patch input.nml as a new or restart run."""

        input_fpath = os.path.join(self.work_path, 'input.nml')

        input_nml = f90nml.read(input_fpath)

        if self.expt.counter == 0 or self.expt.repeat_run:
            input_type = 'n'
        else:
            input_type = 'r'
        input_nml['MOM_input_nml']['input_filename'] = input_type

        f90nml.write(input_nml, input_fpath, force=True)

else:
                    run_runtime = cpl_nml[cpl_group]['runtime']

                # Now write out new run start date and total runtime.
                cpl_nml[cpl_group]['inidate'] = cal.date_to_int(run_start_date)
                cpl_nml[cpl_group][runtime0_key] = total_runtime
                cpl_nml[cpl_group]['runtime'] = int(run_runtime)

                if model.model_type == 'cice':
                    if self.expt.counter and not self.expt.repeat_run:
                        cpl_nml[cpl_group]['jobnum'] = 1 + self.expt.counter
                    else:
                        cpl_nml[cpl_group]['jobnum'] = 1

                nml_work_path = os.path.join(model.work_path, cpl_fname)
                f90nml.write(cpl_nml, nml_work_path + '~')
                shutil.move(nml_work_path + '~', nml_work_path)

        # Now change the oasis runtime. This needs to be done after the others.
        for model in self.expt.models:
            if model.model_type == 'oasis':
                namcouple = os.path.join(model.work_path, 'namcouple')

                s = ''
                with open(namcouple, 'r+') as f:
                    s = f.read()
                    m = re.search(r"^[ \t]*\$RUNTIME.*?^[ \t]*(\d+)", s,
                                  re.MULTILINE | re.DOTALL)
                    assert(m is not None)
                    s = s[:m.start(1)] + str(run_runtime) + s[m.end(1):]

                with open(namcouple, 'w') as f: