I am trying to get the timeline value for particular workitem. I can able to get the iteration value for workitem , but not able to find the timeline value for that particular iteration value. Please check the below code and let me know if any solutions are available.

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dojo.provide("com.xx.rtc.js.estimationtoollink");
dojo.require("com.ibm.team.workitem.api.common.WorkItemAttributes");
(function() {
    dojo.declare("com.xx.rtc.js.estimationtoollink", null, {

        getValue: function(attribute, workItem, configuration) {
    
var WorkItemAttributes= com.ibm.team.workitem.api.common.WorkItemAttributes;


var state=workItem.getValue( WorkItemAttributes.STATE );
var category=workItem.getValue(WorkItemAttributes.FILED_AGAINST);
var workitemid= workItem.getValue(WorkItemAttributes.ID);
var iteration= workItem.getValue(WorkItemAttributes.PLANNED_FOR);
return "http://sgp-v-0021u.sgp.apac.bosch.com/Estimate/estimation" + "/"+workitemid+ "/"+category;
        }
    });
})();