# -*- coding: utf-8 -*-
from openerp import fields,models

class Session(models.Model):
    _name = 'openacademy.session'

    name = fields.Char(required=True)
    start_date = fields.Date()
    duration = fields.Float(digits=(6,2), help="Duration in days")
    seats = fields.Integer(string="Number of seats")
    instructor_id = fields.Many2one('res.partner', string="Instructor")
    course_id = fields.Many2one('openacademy.course',
        ondelete='cascade', string="Course", required=True)
    attendee_ids = fields.Many2many('res.partner', string='Attendees')

# -*- coding: utf-8 -*-
from openerp import fields,models

class Session(models.Model):
    _name = 'openacademy.session'

    name = fields.Char(required=True)
    start_date = fields.Date()
    duration = fields.Float(digits=(6,2), help="Duration in days")
    seats = fields.Integer(string="Number of seats")

    instructor_id = fields.Many2one('res.partner', string="Instructor", 
	domain = ['|', 
	('instructor', '=', True), 
	('category_id.name', 'ilike', "Teacher")])
    course_id = fields.Many2one('openacademy.course',
        ondelete='cascade', string="Course", required=True)
    attendee_ids = fields.Many2many('res.partner', string='Attendees')

Add domain ir and ilike