product_ids = self.pool.get('product.product').search(cr, uid, [], limit=5)
for p in self.pool.get('product.product').browse(cr, uid, product_ids):
    invoice_lines.append((0, 0, {'product_id': p.id, 'name': p.name,
        'account_id': p.categ_id.property_account_income_categ.id}))
res['value']['invoice_line'] = invoice_lines
return res
How to load one to many children on onchange event?