UpdateProcessWorkItemType.
        [Preview API] Updates a work item type of the process.
        :param :class:`<UpdateProcessWorkItemTypeRequest> <azure.devops.v5_0.work_item_tracking_process.models.UpdateProcessWorkItemTypeRequest>` work_item_type_update:
        :param str process_id: The ID of the process
        :param str wit_ref_name: The reference name of the work item type
        :rtype: :class:`<ProcessWorkItemType> <azure.devops.v5_0.work_item_tracking_process.models.ProcessWorkItemType>`

def update_process_work_item_type(self, work_item_type_update, process_id, wit_ref_name):
        """UpdateProcessWorkItemType.
        [Preview API] Updates a work item type of the process.
        :param :class:`<UpdateProcessWorkItemTypeRequest> <azure.devops.v5_0.work_item_tracking_process.models.UpdateProcessWorkItemTypeRequest>` work_item_type_update:
        :param str process_id: The ID of the process
        :param str wit_ref_name: The reference name of the work item type
        :rtype: :class:`<ProcessWorkItemType> <azure.devops.v5_0.work_item_tracking_process.models.ProcessWorkItemType>`
        """
        route_values = {}
        if process_id is not None:
            route_values['processId'] = self._serialize.url('process_id', process_id, 'str')
        if wit_ref_name is not None:
            route_values['witRefName'] = self._serialize.url('wit_ref_name', wit_ref_name, 'str')
        content = self._serialize.body(work_item_type_update, 'UpdateProcessWorkItemTypeRequest')
        response = self._send(http_method='PATCH',
                              location_id='e2e9d1a6-432d-4062-8870-bfcb8c324ad7',
                              version='5.0-preview.2',
                              route_values=route_values,
                              content=content)
        return self._deserialize('ProcessWorkItemType', response)