I am trying to make an automation in my model through code but I don't know if I am missing something because I add what I found on Google but at the end of a month it is not restored. I wish that through an accountant that I already have the method count the sales made in a month, that currently makes it but at the end of the month it continues adding the sales of the previous month and that I do not want, since the idea is that at the end of a month sales made in a month resume and start at 0. The code I have is as follows:

<data noupdate = "1">

        <record forcecreate = "True" id = "vendor_monthly_counter" model = "ir.cron">
           <field name = "name"> Monthly worker accountant </field>
           <field eval = "True" name = "active" />
           <field name = "user_id" ref = "base.user_root" />
           <field name = "interval_number"> 1 </field>
           <field name = "interval_type"> months </field>
           <field name = "numbercall"> - 1 </field>
           <field ref = "model_proyecto_rc_trabajador" name = "model_id" />
            <field name = "state"> code </field>
           <field name = "code"> model.get_realized_sales () </field>
           <field eval = "False" name = "doall" />
           <field name = "function"> True </field


py get_realized_sales


class worker(models.Model):
    _name = 'project_rc.worker'
    _rec_name = 'name'

    name = fields.Char(string="Name", required=True)
    charge = fields.Selection(
        [('seller', 'Seller'), ('cashier', 'Cashier')],
        string="Cargo", required=True)
    sales_counter = fields.Integer(
        string="Sales made", compute="get_realized_sales", store=True)
    document_ids = fields.One2many(
        comodel_name='project_rc.document', inverse_name='worker_id',
        string='Invoice', required=true)

    @api.depends ('document_ids')
    def get_realized_sales(self):
        for rec in self:
            document = rec.document_ids.filtered(
                lambda r: r.type_movimiento_id and\
                    r.type_movement_id.type_movement == 'sale')
            rec.sales_counter = len(document)

What could I miss, some py? and how would that py be?