Write a function that takes a list of elements and returns only the integers.
return_only_integer([9, 2, "space", "car", "lion", 16]) ➞ [9, 2, 16]
return_only_integer(["hello", 81, "basketball", 123, "fox"]) ➞ [81, 123]
return_only_integer([10, "121", 56, 20, "car", 3, "lion"]) ➞ [10, 56, 20, 3]
return_only_integer(["String", True, 3.3, 1]) ➞ [1]
N/A