code: public static PrefHelper getInstance(Context context) {
          if (prefHelper_ == null) {
              prefHelper_ = new PrefHelper(context);
          }
          return prefHelper_;
      }
docs: <p>Singleton method to return the pre-initialised, or newly initialise and return, a singleton
  object of the type {@link PrefHelper}.</p>
  
  @param context The {@link Context} within which the object should be instantiated; this
  parameter is passed to the private {@link #PrefHelper(Context)}
  constructor method.
  @return A {@link PrefHelper} object instance.