Sorry I don't, I just know is technically possible. Take this request for example:
Here is an example though the Genesys Support Phone, you should be able to reproduce it though code:
23:16:31.077 Trc 04541 RequestInitiateTransfer received from 3004 (23af - SPv7203ST)
message RequestInitiateTransfer
AttributeThisDN 5551
AttributeConnID 00a501891d8f8c8a
AttributeOtherDN '5553'
AttributeReferenceID 6
23:16:31.077 Int 04543 Interaction message "RequestInitiateTransfer" received from 3004 (" - SPv7203ST")
@23:16:31.1080 [0] 7.2.009.00 distribute_event: message EventHeld
@23:16:31.1390 [0] 7.2.009.00 distribute_response: message EventDialing
@23:16:31.1390 [0] 7.2.009.00 distribute_event: message EventRinging
@23:16:31.1390 [0] 7.2.009.00 distribute_event: message EventEstablished
23:16:31.077 Trc 04541 RequestInitiateTransfer received from 3004 (23af - SPv7203ST)
message RequestInitiateTransfer
AttributeThisDN 5551
AttributeConnID 00a501891d8f8c8a
AttributeOtherDN '5553'
AttributeReferenceID 6
23:16:31.077 Int 04543 Interaction message "RequestInitiateTransfer" received from 3004 (" - SPv7203ST")
@23:16:31.1080 [0] 7.2.009.00 distribute_event: message EventHeld
@23:16:31.1390 [0] 7.2.009.00 distribute_response: message EventDialing
@23:16:31.1390 [0] 7.2.009.00 distribute_event: message EventRinging
@23:16:35.6080 [0] 7.2.009.00 distribute_event: message EventEstablished
23:16:53.983 Trc 04541 RequestCompleteConference received from 3004 (23af - SPv7203ST)
message RequestCompleteConference
AttributeThisDN 5551
AttributeConnID 00a501891d8f8c8a
AttributeConferenceConnID 00a501891d8f8c8c
AttributeReferenceID 8
23:17:06.264 Trc 04541 RequestDeleteFromConference received from 3004 (23af - SPv7203ST)
message RequestDeleteFromConference
AttributeThisDN 5551
AttributeOtherDN '5553'
AttributeConnID 00a501891d8f8c8a
AttributeReferenceID 9
23:17:06.264 Int 04543 Interaction message "RequestDeleteFromConference" received from 3004 (" - SPv7203ST")
So in Summary, extension 5551 called 5552, conferenced in 5553 and then droped 5553 from the call.