michel_coworking/coworking_relation/views/relation_views.xml

<?xml version="1.0" encoding="utf-8"?>

<odoo>

<!-- Form -->
<record id="view_form_relation" model="ir.ui.view">
  <field name="name">Relation Form</field>
  <field name="model">coworking.relation</field>
  <field name="arch" type="xml">
    <form string="event">
      <sheet>
        <group name="group_top">
          <group name="group_left">
            <field name="coworker1" domain="[('id', '!=', coworker2)]" />
            <field name="coworker2" domain="[('id', '!=', coworker1)]" />
            <field name="relation" />
          </group>
        </group>
      </sheet>
    </form>
  </field>
</record>

<!-- Tree -->
<record id="view_tree_relation" model="ir.ui.view">
  <field name="name">relation Tree</field>
  <field name="model">coworking.relation</field>
  <field name="arch" type="xml">
    <tree editable="True">
      <field name="coworker1" domain="[('id', '!=', coworker2)]" />
      <field name="coworker2" domain="[('id', '!=', coworker1)]" />
      <field name="relation" />
    </tree>
  </field>
</record>

</odoo>