code: public static String getFileName(final ConfigurationSourceKey source){
  		//ensure an exception is thrown if we are not file.
  		if (source.getType()!=ConfigurationSourceKey.Type.FILE)
  			throw new AssertionError("Can only load configuration sources with type "+ConfigurationSourceKey.Type.FILE);
  		return source.getName()+ '.' +source.getFormat().getExtension();
  	}
docs: Returns the file name for the given source key.
  
  @param source configuration source key
  @return the file name for the given source key