code: public byte[] getPrivate() {
          keyNotNull(pair.getPrivate());
          Key key = pair.getPrivate();
          return getKeyBytes(key);
      }
docs: Get the byte representation of the private key as it is returned by the underlying security library. This is
  NOT the byte array that contains the algorithm at the start. This is the key in raw format.
  
  @return the key as bytes