sr=session.xenapi.SR.get_by_name_label("DVD drives")
record_dvd=session.xenapi.SR.get_record(sr[0])
VDI_dvd=record_dvd["VDIs"]
vbdconnectcd={'VDI':VDI_dvd[0],
                  'VM':VM_ref,
                  'userdevice':"1",
                  'mode':"RO",
                  'type':"cd",
                  'bootable':True,
                  'unpluggable':True,
                  'empty':False,
                  'other_config':{},
                  'qos_algorithm_type':'',
                  'qos_algorithm_params':{}}
vbdref1=session.xenapi.VBD.create(vbdconnectcd)