public String toString() {
		StringBuilder sb = new StringBuilder();
		// feature first
		for (double value : mFeatures) {
			sb.append(value + " ");
		}
		sb.append("=====> ");
		// label second, features and label are separated by =====>
		sb.append(mLabel);
		
		return sb.toString().trim();   // trim all the whitespace before the string or after the string
	}