docs: @Nullable
      @FundingType
      public static String asFundingType(@Nullable String possibleFundingType) {
          if (possibleFundingType == null || TextUtils.isEmpty(possibleFundingType.trim())) {
              return null;
          }
  
          if (Card.FUNDING_CREDIT.equalsIgnoreCase(possibleFundingType)) {
              return Card.FUNDING_CREDIT;
          } else if (Card.FUNDING_DEBIT.equalsIgnoreCase(possibleFundingType)) {
              return Card.FUNDING_DEBIT;
          } else if (Card.FUNDING_PREPAID.equalsIgnoreCase(possibleFundingType)) {
              return Card.FUNDING_PREPAID;
          } else {
              return Card.FUNDING_UNKNOWN;
          }
      }