func_code: def union(a, b):
      c = {}
      i = 0
      while i < len(a):
          sys.stdout.write(a[i])
          c[a[i]] = True
          i = i + 1
      i = 0
      while i < len(seen):
          if b[i] not in seen:
              sys.stdout.write(b[i])
              c[b[i]] = True
              i = i + 1
              print(c)
      if __name__ == '__main__':
          print(union([1, 2, 3], [3, 4, 5]))