private String convertPrepareData(String prepareData) {
        prepareData = prepareData.replaceAll(ESCAPE_FILL_PREFIX, FILL_PREFIX);
        prepareData = prepareData.replaceAll(ESCAPE_FILL_SUFFIX, FILL_SUFFIX);
        return prepareData;
    }
To prepare data

@param cell          cell
@param rowIndex      row index
@param columnIndex   column index
@param firstRowCache first row cache
@return Returns the data that the cell needs to replace
fastexcel-core/src/main/java/cn/idev/excel/write/executor/ExcelWriteFillExecutor.java