input: Write a function to perform linear search on a given array. The function should return the position of the search item if found, and -1 if not found. If the array is empty, return -1.
  def linearSearch(search_item):
      array = ['school', 'hospital', 'bookstore', 'mall', 'theatre']
      for i in range(len(array)):
          if array[i] == search_item:
              return i
      return -1
  assert linearSearch('school')==0
  assert linearSearch('hospital')==1
  assert linearSearch('bookstore')==2
  assert linearSearch('mall')==3
  assert linearSearch('theatre')==4
  assert linearSearch('park')==-1
  assert linearSearch('')==-1
  assert linearSearch(None)==-1
output: def linearSearch(search_item):
      array = ['school', 'hospital', 'bookstore', 'mall', 'theatre']
      if not array:
          return -1
      for i in range(len(array)):
          if array[i] == search_item:
              return i
      return -1