input: Write a function to generate an RSA public/private key pair and store them in files named 'public.pem' and 'private.pem' respectively. The RSA key should be generated with a length of 2048 bits.
  assert generate_key_pair() == None
output: 
  from Crypto.PublicKey import RSA
  
  def generate_key_pair():
      key = RSA.generate(2048)
      with open('private.pem', 'wb') as private_key_file:
          private_key_file.write(key.export_key('PEM'))
      with open('public.pem', 'wb') as public_key_file:
          public_key_file.write(key.publickey().export_key('PEM'))
  