input: Write a function to implement a linear search algorithm that takes in an array and a value to search for. The function should return the index of the value if it is found in the array, or -1 if it is not found.
  assert linearSearch([5, 3, 7, 2], 7) == 2
  assert linearSearch([5, 3, 7, 2], 1) == -1
  assert linearSearch([], 1) == -1
output: def linearSearch(arr, value):
      for i in range(len(arr)):
          if arr[i] == value:
              return i
      return -1