input: 
  def linearSearch(search_item: str, array: List[str]) -> int:
      """ Perform a linear search on a given array to find the index of the search_item.
      If the item is found, return its index. If the item is not found, return -1.
      >>> linearSearch('bookstore', ['school', 'hospital', 'bookstore', 'mall', 'theatre'])
      2
      >>> linearSearch('restaurant', ['school', 'hospital', 'bookstore', 'mall', 'theatre'])
      -1
      """
      for i in range(len(array)):
          if array[i] == search_item:
              return i
      return -1
  
output:     for i in range(len(array)):
          if array[i] == search_item:
              return i
      return -1