code: public void addScalar(int k) {
  		Set<O> remove = new HashSet<>();
  		for (O o : multiplicities.keySet()) {
  			setMultiplicity(o, multiplicity(o) + k);
  			if (multiplicity(o) < 1) {
  				remove.add(o);
  			}
  		}
  		for (O o : remove) {
  			remove(o);
  		}
  	}
docs: Scalar addition.<br>
  Adds k to the multiplicity of all objects.<br>
  In case the multiplicity of an object falls below 1, it is removed.
  
  @param k The value to add.