code: public TableFilter getFilter(final UITableHeader _uitableHeader)
          throws EFapsException
      {
          TableFilter ret = this.filters.get(_uitableHeader.getFieldName());
          if (ret != null && ret.getUiTableHeader() == null) {
              ret = new TableFilter(_uitableHeader);
              this.filters.put(_uitableHeader.getFieldName(), ret);
          }
          return ret;
      }
docs: Method to get a Filter from the list of filters belonging to this
  UITable.
  
  @param _uitableHeader UitableHeader this filter belongs to
  @return filter
  @throws EFapsException on error