Hi,

workorder_count = fields.Integer('# Work Orders', compute='_compute_workorder_count')

The above line is field declaration and if you have to increment the value on the field workorder_count, write a function in the name you have mentioned in the compute "_compute_workorder_count".

@api.depends('workorder_count')
def _compute_workorder_count(self):   
     self.workorder_count += 1

Thanks