This is my mail.message pythoncode

values = {
    'body': nl2br("""<b style="font-weight:600">Reject Reason:</b> """),
    'model': self._name,
    'message_type': 'comment',
    'no_auto_thread': False,
    'res_id': self.id,
    'notification': True,
}
mail_id = self.env['mail.message'].create(values)
form_view = self.env.ref('hr_timesheet_sheet.view_message_form_log')
context = dict(self.env.context)
context['form_view_initial_mode'] = 'edit'

return {'name': _('Reject Reason'),
        'type': 'ir.actions.act_window',
        'view_type': 'form',
        'view_mode': 'form',
        'res_model': 'mail.message',
        'res_id': mail_id.id,
        'views': [(form_view.id, 'form'), ],
        'target': 'new',
        }
api.multi
def refuse(self):
mail_values_refuse = {
    # 'email_from': self.employee_id,work_email,
    'email_to': 'self.employee_idwork_email',
    'subject': 'rejected by' + self.employee_id.parent_id.name,
    'body_html': '',                                                         '//I need to display Here mail.message body content How?
    'notification': True,
}
mail = self.env['mail.mail'].create(mail_values_refuse)
mail.send()


                                                                This is my mail.message xml code

<record model="ir.ui.view" id="view_message_form_log">
    <field name="name">mail.message.form</field>
    <field name="model">mail.message</field>
    <field name="priority">25</field>
    <field name="arch" type="xml">
        <form string="Message">
            <sheet>
                <field name="body" options="{'style-inline': true}"/>
                <footer>
                <button name="refuse" type="object" string="Submit Reason"
                    confirm="Are you sure ??"
                    class="oe_highlight"/>
                <button string="Discard" class="btn-default" special="cancel"/>
            </footer>

            </sheet>
        </form>
    </field>
</record>

My question is , If I click save button (save button is placed inside 'mail.message' class) the 'body 'content of mail.message will be passed to the mail.mail 'body_html'.

It shows an error like mail.message doesn't have

refuse

How to Solve it??