input: Write a function to create a linked list in Python using classes. The functions should include a Node class to represent the node in the linked list, and a LinkedList class to represent the entire linked list. The LinkedList class should have a method to print the list. Also, provide a sample usage of the linked list with three nodes.
  assert linked_list.print_list == 1 2 3
  assert linked_list.head.data == 1
  assert linked_list.head.next.data == 2
  assert linked_list.head.next.next.data == 3
  assert linked_list.head.next.next.next == None
output: class Node:
      def __init__(self, data):
          self.data = data
          self.next = None
  
  class LinkedList:
      def __init__(self):
          self.head = None
  
      def print_list(self):
          temp = self.head
          while temp:
              print(temp.data, end=" ")
              temp = temp.next