code: public String marshall() {
          if (0 == this.num_items) {
              return "";
          }
          boolean shouldPrepend = false;
          StringBuilder output = new StringBuilder(10 * this.num_items);
          // walk through the list of simple values (no key=value) first
          Iterator<String> i = this.genericValues.iterator();
          while (i.hasNext()) {
              if (shouldPrepend) {
                  output.append(this.mySep);
                  output.append(' ');
              }
              output.append(i.next());
              shouldPrepend = true;
          }
          // now walk through the list of key=value pairs, where value may actually
          // be multiple values
          i = this.values.keySet().iterator();
          while (i.hasNext()) {
              String key = i.next();
              List<String> vals = this.values.get(key);
              if (null == vals)
                  continue;
              int size = vals.size();
              if (0 == size) {
                  // ignore an empty key
                  continue;
              }
              if (shouldPrepend) {
                  output.append(this.mySep);
                  output.append(' ');
              }
              output.append(key);
              output.append('=');
              if (1 == size) {
                  output.append(vals.get(0));
              } else {
                  // multiple values need to be quote wrapped
                  shouldPrepend = false;
                  output.append('"');
                  for (int count = 0; count < size; count++) {
                      if (shouldPrepend) {
                          output.append(this.mySep);
                          output.append(' ');
                      }
                      output.append(vals.get(count));
                      shouldPrepend = true;
                  }
                  output.append('"');
              }
              shouldPrepend = true;
          }
          if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled()) {
              Tr.debug(tc, "marshalling [" + output.toString() + "]");
          }
          return output.toString();
      }
docs: Take the current data in this handler and create the properly formatted
  string that would represent the header.
  
  @return String (empty string if no values are present)