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