code: @UnstableApi
      public final void setPrivateKeyMethod(OpenSslPrivateKeyMethod method) {
          ObjectUtil.checkNotNull(method, "method");
          Lock writerLock = ctxLock.writeLock();
          writerLock.lock();
          try {
              SSLContext.setPrivateKeyMethod(ctx, new PrivateKeyMethod(engineMap, method));
          } finally {
              writerLock.unlock();
          }
      }
docs: Set the {@link OpenSslPrivateKeyMethod} to use. This allows to offload private-key operations
  if needed.
  
  This method is currently only supported when {@code BoringSSL} is used.
  
  @param method method to use.