Set value to Not assigned via REST API

Set value to Not assigned via REST API

Hi

Trying to set technician and group to not assigned but it doesnt work.
tried this but no succes
operation = EDIT_REQUEST
input_data = <Operation><Details><technician/></Details></Operation> 

The reply is "Request 151912 successfully edited" but no change is made.

How do you set a value to not assigned ?

BR Jesper

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