anchor.diff:        case TelevisionSource.switching:
           break; // must be last in switch statement
       }
  -    throw new TelevisionException('Selected source is too ambiguous', source.toString(), null);
  +    throw new TelevisionException('Selected source is too ambiguous.', source.toString(), null);
     }
   
     // Create a source object to represent a specific TV channel.
  
positive.code:      case '1':
         return true;
      }
      throw new TelevisionErrorResponse('Unknown response to "POWR" message', response, this);
    }
  
    Future<Null> setPower(bool value) async {
  
negative.code:       if (response == 'ERR') {
          if (errorIsNull)
            return null;
          throw new TelevisionErrorResponse('Unexpected response to "$message$argument".', response, this);
        }
        return response;
      } on TelevisionException {
  