code: public static <L, R> MutablePair<L, R> of(final L left, final R right) {
          return new MutablePair<>(left, right);
      }
docs: <p>Obtains an immutable pair of from two objects inferring the generic types.</p>
  
  <p>This factory allows the pair to be created using inference to
  obtain the generic types.</p>
  
  @param <L> the left element type
  @param <R> the right element type
  @param left  the left element, may be null
  @param right  the right element, may be null
  @return a pair formed from the two parameters, not null