code: public static String getOptionalStringParam(JSONObject params, String paramName) {
  		if (params.containsKey(paramName)) {
  			return params.getString(paramName);
  		}
  		return null;
  	}
docs: Gets an optional string param, returning null if the parameter was not found.
  
  @param params the params
  @param paramName the param name
  @return the optional string param