code: private boolean checkFiltered() {	
  		if ((this.hocr.getMetaDataFilter()==null) || (this.hocr.getMetaDataFilter().size()==0)) { // if no filter is defined it does match by definition
  			return true;
  		}
  		if (this.currentWorkbook instanceof XSSFWorkbook) {
  			return checkFilteredXSSF();
  		} else if (this.currentWorkbook instanceof HSSFWorkbook) {
  			return checkFilteredHSSF();
  		} else	{
  			LOG.error("Unknown workbook format. Cannot check if document matches metadata filter");
  			return false;
  		}
  	}
docs: /*
  Check if document matches the metadata filters
  
  @return true, if it matches, false if not