input: Write a function to create a search engine in Python that quickly searches through a given array using linear search. The function should return the position of the item if found or -1 if not found. If the array is empty, the function should return -1.
  assert linearSearch('mall')==3
  assert linearSearch('school')==0
  assert linearSearch('theatre')==4
  assert linearSearch('library')==-1
  assert linearSearch('')==-1
output: def linearSearch(item):
      array = ['school', 'mall', 'park', 'office', 'theatre']
      if not array:
          return -1
      for i in range(len(array)):
          if array[i] == item:
              return i
      return -1