propel: 
    st_product: 
        _attributes: 
            phpName: Product
            isI18N: true
            i18nTable: st_product_i18n
        group_price_id: 
            type: INTEGER
            foreignTable: st_group_price
            foreignReference: id
            onDelete: setnull
        _indexes:
            group_price_idx:    [group_price_id]