code: @Nullable
      public static ApiError parseError(@Nonnull Response<?> response) {
          if (response.isSuccessful()) {
              return null;
          }
  
          try {
              return parseError(response.errorBody().string(), response.code(), response.message());
          } catch (IOException e) {
              return new ApiError(null, response.code(), "Unknown Error");
          }
      }
docs: Parses a {@link Response} into an {@link ApiError}.
  
  @param response the {@link Response} to parse.
  @return an {@link ApiError} if parsable, or {@code null} if the response is not in error.