static <T> Error<T> of(final LossFunction<T> loss) {
		requireNonNull(loss);
		return (p, c, e) -> loss.apply(c, e);
	}
Creates an error function which only uses the given {@code loss} function
for calculating the program error

@param <T> the sample type
@param loss the loss function to use for calculating the program error
@return an error function which uses the loss function for error
        calculation
@throws NullPointerException if the given {@code loss} function is
        {@code null}
jenetics.prog/src/main/java/io/jenetics/prog/regression/Error.java