input: Write a python function to generate an RSA key pair and save them to 'public.pem' and 'private.pem'.
  assert os.path.exists('public.pem')
  assert os.path.exists('private.pem')
output: def generate_rsa_key_pair():
      from Crypto.PublicKey import RSA
      from Crypto.Random import get_random_bytes
  
      key = RSA.generate(2048)
      private_key = key.export_key()
      public_key = key.publickey().export_key()
  
      with open('private.pem', 'wb') as priv_file:
          priv_file.write(private_key)
  
      with open('public.pem', 'wb') as pub_file:
          pub_file.write(public_key)