class a(models.Mocel):
    _name='a'
    master = field.Char()
    slave = field.One2many('b','a_id')

class b(models.Model):
    _name='b'
    a_id=field.Many2one('a')
    c_id=field.Many2one('c')

class c(models.Model):
    _name='c'
    code=field.Char()

and the view for model "a"

<field name="master"/>
<field name="slave">
    <tree editable="bottom">
        <field name="c_id"/>
    </tree>
</field>

I need to filter "c" so that a.master=c.code so I tryed:

@api.onchange('master')
def onchange_master(self):
    return {'domain': {'slave.c_id': [('code','=',self.master)]}}

and

@api.onchange('master')
def onchange_master(self):
    return {'domain': {'slave': [('code','=',self.master)]}}

and

@api.onchange('master')
def onchange_master(self):
    return {'domain': {'c_id': [('code','=',self.master)]}}

but it just doesn't set the domain for c_id field. Is there any way to achieve this, or it is just not possible?