code: @Override
      public String readValue(String column, int line) throws TechnicalException {
          final int colIndex = columns.indexOf(column);
          final Sheet sheet = workbook.getSheetAt(0);
          final Row row = sheet.getRow(line);
          final Cell cell = row.getCell(colIndex);
          if (cell == null) {
              return "";
          } else {
              return readCell(cell);
          }
      }
docs: {@inheritDoc}