code: protected void warning(String message, EObject source, EStructuralFeature feature) {
  		getContext().getMessageAcceptor().acceptWarning(
  				MessageFormat.format(getErrorMessageFormat(), message),
  				source,
  				feature,
  				ValidationMessageAcceptor.INSIGNIFICANT_INDEX,
  				IssueCodes.INVALID_EXTRA_LANGUAGE_GENERATION);
  	}
docs: Generate a warning for the extra-language.
  
  <p>This function generates an error, a warning, or an information depending on the extra-language generation's
  configuration.
  
  @param message the warning message.
  @param source the source of the error.
  @param feature the structural feature.