docs: @Nullable
      public Token createAccountTokenSynchronous(
              @NonNull final AccountParams accountParams,
              @Nullable String publishableKey)
              throws AuthenticationException,
              InvalidRequestException,
              APIConnectionException,
              APIException {
          String apiKey = publishableKey == null ? mDefaultPublishableKey : publishableKey;
          if (apiKey == null) {
              return null;
          }
          validateKey(publishableKey);
          RequestOptions requestOptions = RequestOptions.builder(
                  publishableKey, mStripeAccount, RequestOptions.TYPE_QUERY)
                  .build();
          try {
              return mApiHandler.createToken(
                      accountParams.toParamMap(),
                      requestOptions,
                      Token.TYPE_ACCOUNT
              );
          } catch (CardException exception) {
              // Should never occur. CardException is only for card related requests.
          }
          return null;
      }