I need to get the quantity for each product for a specific location in the BOM structure tree view. My location name is "Raw Materials". 

class mrp_bom(osv.osv):
    _inherit = "mrp.bom"
             

    def _get_raw_qty(self, cr, uid, ids, field_name, args, context=None):
        
        res = {}

        for record in self.browse(cr, uid, ids,context=context):
        

            qty=<<<<<need quantity for product at specific location>>>>>>
            res[record.id] = qty
        return res
        
    _columns = {
        'qty_available': fields.related('product_id', 'qty_available', type="float", relation="product.product", string="Qty FG"),
        'cost_price': fields.related('product_id', 'cost_price', type="float", relation="product.product", string="Cost"),
        'standard_price': fields.related('product_id', 'standard_price', type="float", relation="product", string="Std Price"),
        'qty_raw': fields.char('Qty Raw', select=True, help='HELP text when hovering over the label in openERP'),
        'qty_raw': fields.function( _get_raw_qty, method=True, type='float', string='Raw Qty', store=False)}

        
mrp_bom()