code: public void setCustomStringGenerator(Function<List<SubunitCluster>,String> customStringGenerator) {
  		this.strategy = StringOverflowStrategy.CUSTOM;
  		this.customStringGenerator = customStringGenerator;
  	}
docs: Let a user-defined function handle the entire string representation of a stoichiometry.
  @param customStringGenerator
  A function which accepts a list of subunit clusters and returns a string.