code: @Override
      public String setParameterValue(String parameterName, String parameterValue) {
          // don't try to store a null value
          if (parameterValue == null) return null;
          return (String) parameters.put(parameterName, parameterValue);
      }
docs: Set a channel parameter value.
  
  @param parameterValue a <code>String</code> value
  @param parameterName a <code>String</code> value
  @return a <code>String</code> value that was set.