code: public static String writeConfigurationFile( FileDefinition relationsFile, boolean writeComments, String lineSeparator ) {
  		return new FileDefinitionSerializer( lineSeparator ).write( relationsFile, writeComments );
  	}
docs: Writes a model into a string.
  @param relationsFile the relations file
  @param writeComments true to write comments
  @param lineSeparator the line separator (if null, the OS' one is used)
  @return a string (never null)