How do I call a method in ir.rule domain in Odoo?

I'd like to create a record rule for my app.

Here is my XML:

<record model="ir.rule" id="ir_rule_something"> 
    <field name="name">something</field> 
    <field name="model_id" ref="model_something"/> 
    <field name="domain_force">[('agent','in',function_that_return_list_of_ids)]</field> 
    <field name="perm_read" eval="True"/> 
    <field name="perm_write" eval="False"/> 
    <field name="perm_unlink" eval="False"/> 
    <field name="perm_create" eval="False"/> 
</record>

I would like the function_that_return_list_of_ids to return a list of id. Where do I put the method and how do I call it?

The easiest way will be for you to override _eval_context or _eval_context_for_combinations in ir.rule itself.

class MyIrRule(models.Model):
    _inherit ="ir.rule"

    @api.model
    def _eval_context(self):
        context = super(MyIrRule,self)._eval_context()
        context.update(function_of_ids=function_of_ids)

In this example, function_of_ids is not a method but a simple function.