input: 
  def removeDuplicates(array):
      """ Optimize the following Python code to use built-in functions.
      >>> removeDuplicates([1, 2, 3, 4, 4, 5, 6, 6])
      [1, 2, 3, 4, 5, 6]
      >>> removeDuplicates(['a','b','a','c','d','d'])
      ['a', 'b', 'c', 'd']
      """
  
output:     return list(dict.fromkeys(array))