input: def optimize_linear_search(arr, x):
      """Optimize the provided linear search function by using the enumerate function.
      This will make the code more readable and concise.
      >>> optimize_linear_search([3, 5, 1, 9, 2], 1)
      2
      >>> optimize_linear_search([3, 5, 1, 9, 2], 4)
      -1
      """
output:     for i, value in enumerate(arr):
          if value == x:
              return i
      return -1