input: Write a function to optimize the given Python code that removes duplicates from an array using built-in functions. The function should take an array as input and return an array with all duplicate elements removed.
  assert removeDuplicates([1, 2, 2, 3, 4, 4, 5])==[1, 2, 3, 4, 5]
  assert removeDuplicates([1, 1, 1, 1])==[1]
  assert removeDuplicates([1, 2, 3, 4, 5])==[1, 2, 3, 4, 5]
  assert removeDuplicates([])==[]
  assert removeDuplicates([5, 5, 5, 6, 7, 7, 8, 8, 8])==[5, 6, 7, 8]
output: def removeDuplicates(arr):
      return list(dict.fromkeys(arr))