def chooseHighestFromTuple(arr):
    """
    Pick the id of the highest element of a list of tuples of the form (id, key),
        where they key determines which value is the highest
    :param arr: The array of elements
    :return: A tuple of the form (id, key) of the element with the highest key
    """
    high = 0
    for i, a in enumerate(arr):
        if a[1] > arr[high][1]:
            high = i
    return arr[high]