How to add a custom RSA key pair to a .pem file

Question

I created a custom RSA key pair just for test purposes in python. I want to add the private key and public key to a .pem file but I didnt find anything in my research. All i found is people generating a RSA key pair from a library. I have the e, d and n variables for the public key[e, n] and private key[d, n].