Hello.. I have database of suppliers and I want to create input form with general information about supplier and editable list of supplier products. I've tried to create form like this

<record id="view_partner_form" model="ir.ui.view">
        <field name="name">res.partner.form</field>
        <field name="model">res.partner</field>
        <field eval="1" name="priority"/>
        <field name="arch" type="xml">
            <form string="Partners" version="7.0">
            <sheet>
                <group>
                    <group>
                        <field name="company_name"/>
                        <field name="address"/>
                        <field name="website" widget="url"/>
                        ......
                                                    ......
                    </group>
                </group>
                <notebook>
                  <page string="Products">
                  <field name="products_line">  
                    <tree string="Products">
                        <field name="products"/>
                        <field name="price"/>
                    </tree>
                  </field>
                   </page>  
                </notebook>
               </sheet>
             </form>
        </field>
 </record>

But it gives error - Invalid XML for view Architecture or show nothing I think it's related to class description in python code, but I don't what exactly os this.