Hi,

If you are looking to create a sequence for the model maintenance request , like in the sales, like SO001,SO002 etc,

In the XML file create a sequence like this,

<record id="seq_material_request" model="ir.sequence">
    <field name="name">Material Request</field>
    <field name="code">material.request</field>
    <field name="prefix">MR</field>
    <field name="padding">3</field>
    <field name="company_id" eval="False"/>
</record>

Then,

You have to define a field in python in this model and you have to write the value to it, for that

name = fields.Char(string='Request  No', required=True, copy=False, readonly=True,
                   index=True, default=lambda self: _('New'))

@api.model
def create(self, vals):
    """Overriding the create method and assigning the the sequence for the record"""
    if vals.get('name', _('New')) == _('New'):
        vals['name'] = self.env['ir.sequence'].next_by_code('material.request') or _('New')
    res = super(ClassName, self).create(vals)
    return res

Thanks