input: Write a function to remove all duplicates from an array of strings and return the resulting array with the strings in their original order of occurrence. If the input array is empty, return an empty array.
  assert removeDuplicates(['a', 'b', 'a', 'c', 'c', 'd'])==['a', 'b', 'c', 'd']
  assert removeDuplicates(['x', 'y', 'x', 'y', 'z'])==['x', 'y', 'z']
  assert removeDuplicates(['p', 'q', 'r', 's'])==['p', 'q', 'r', 's']
  assert removeDuplicates([])==[]
output: def removeDuplicates(arr):
      seen = set()
      result = []
      for item in arr:
          if item not in seen:
              seen.add(item)
              result.append(item)
      return result