onBeforeCall and onAfterCall

I see these two functions used in javascript node and written some code under these functions ( they defined the function ) 

like for example: 

in the javascript node of a workflow they added : 

function onBeforeCall() {
logInfo("task.activity:" + task.activity);

if ((activity.img.indexOf("nms:activities/delivery.png") != -1) || (activity.img.indexOf("nms:activities/email.png") != -1) || ((activity.img.indexOf("nms:activities/notification.png") != -1) && (task.activity == 'notification'))) {

// some code 

}

but i can't see where they called this function. Are these two functions called automatically OR these two functions are inbuilt functions. Where can i see them called but the code which is under this function gets executed when the workflow runs. 

i can see in some places in logs onAfterCall : 

Is there any documentation available on these functions.