input: Write a python function to run two threads that print numbers from 1 to 10 with a delay of 1 second between each number.
  assert run_threads() == None
output: import threading
  import time
  
  def print_numbers():
      for i in range(1, 11):
          print(i)
          time.sleep(1)
  
  def run_threads():
      thread1 = threading.Thread(target=print_numbers)
      thread2 = threading.Thread(target=print_numbers)
      
      thread1.start()
      thread2.start()
      
      thread1.join()
      thread2.join()