code: @PublicEvolving
  	public String getString(ConfigOption<String> configOption, String overrideDefault) {
  		Object o = getRawValueFromOption(configOption);
  		return o == null ? overrideDefault : o.toString();
  	}
docs: Returns the value associated with the given config option as a string.
  If no value is mapped under any key of the option, it returns the specified
  default instead of the option's default value.
  
  @param configOption The configuration option
  @return the (default) value associated with the given config option