code: public SslContextBuilder keyManager(InputStream keyCertChainInputStream, InputStream keyInputStream) {
          return keyManager(keyCertChainInputStream, keyInputStream, null);
      }
docs: Identifying certificate for this host. {@code keyCertChainInputStream} and {@code keyInputStream} may
  be {@code null} for client contexts, which disables mutual authentication.
  
  @param keyCertChainInputStream an input stream for an X.509 certificate chain in PEM format
  @param keyInputStream an input stream for a PKCS#8 private key in PEM format