You can use many2one with domain for this purpose.

You need create object "Leave" like:

    _columns = {
        'name': fields.char('Leave'),
        'type': fields.char('Type'),
        'interval': fields.char('interval'),
        }

Then create records for "Leave" with all available combination type and interval.

In object, where you need selection field, define instead many2one to "Leave" object (for example: leave_id).
And define selection filed for type (for example: type).
Now you can dinamically select available leaves, depend from type, like:

    <field name="type"/>
    <field name="leave_id" domain="[('type','=',type)]"/>

Hi, 

You can follow following link for this:

https://youtu.be/GPhgxxwprA4

Hope it helps,

Thanks