input: Write a function to implement a linear search in Python to quickly search through a given array. The function should take a search item as input, loop through the array, and return the position of the search item if found. If the search item is not found, the function should return -1. After defining the function, take an input from the user for the search item and print the result accordingly.
  assert linearSearch('bookstore')==2
  assert linearSearch('mall')==3
  assert linearSearch('library')==-1
  assert linearSearch('school')==0
  assert linearSearch('theatre')==4
output: def linearSearch(search_item):
      array = ['school', 'bookstore', 'bookstore', 'mall', 'theatre']
      for i in range(len(array)):
          if array[i] == search_item:
              return i
      return -1