How to check for existence of a certain array in another array?

At some point in my system, I need to consume a method that returns an array, which can contain arrays.

I need to feed a second array with data contained in the main array . See example?

arrayRetorno[0] = item[i].tasks[0].colleagueId;

There may be some cases where the array tasks does not exist, so how do you check for an array task / em> item ?