input: Write a function to perform linear search on a given array. The function should return the position of the search item if found, otherwise return -1. If the given array is empty, return -1.
  
  def linearSearch(search_item, array):
      if not array:
          return -1
      for i in range(len(array)):
          if array[i] == search_item:
              return i
      return -1
  
  assert linearSearch('bookstore', ['school', 'hospital', 'bookstore', 'mall', 'theatre'])==2
  assert linearSearch('theatre', ['school', 'hospital', 'bookstore', 'mall', 'theatre'])==4
  assert linearSearch('library', ['school', 'hospital', 'bookstore', 'mall', 'theatre'])==-1
  assert linearSearch('mall', ['school', 'hospital', 'bookstore', 'mall', 'theatre'])==3
  assert linearSearch('hospital', [])==-1
output: def linearSearch(search_item, array):
      if not array:
          return -1
      for i in range(len(array)):
          if array[i] == search_item:
              return i
      return -1