input: Write a python function to remove duplicates from an array.
  assert remove_duplicates([1, 2, 3, 3, 3, 4, 5, 6]) == {1, 2, 3, 4, 5, 6}
  assert remove_duplicates([10, 20, 30, 10, 20, 30, 40]) == {10, 20, 30, 40}
  assert remove_duplicates([1, 1, 1, 1, 1, 1, 1]) == {1}
output: def remove_duplicates(arr):
      return set(arr)