So i have this function and i'm getting error for some reason

def _product_inc_out_qty(self, cr, uid, ids, field_names=None, arg=False, context=None):
            res = {}
            for move in self.browse(cr, uid, ids, context=context):
                res[move.id] = {
                    'incoming_qty': 0.0,
                    'outgoing_qty': 0.0,
                }
                
                res[move.id]['incoming_qty'] = move.product_id.incoming_qty
                res[move.id]['outgoing_qty'] = move.product_id.outgoing_qty
            return res
    
    _columns = {
                'incoming_qty': fields.function(_product_inc_out_qty, type='float',method=True,
            digits_compute=dp.get_precision('Product Unit of Measure'),
            string='Incoming'
        ),
        'outgoing_qty': fields.function(_product_inc_out_qty, type='float',method=True,
            digits_compute=dp.get_precision('Product Unit of Measure'),
            string='Outgoing'
        ),
    }


and i'm getting this error 

    value = float(value or 0.0)
TypeError: float() argument must be a string or a number