code: public MaxentModel getModel (ModelDomain domain) {
  	if (map.containsKey(domain)) {
  	    return (MaxentModel)map.get(domain); 
  	}  else {
  	    throw new NoSuchElementException("No model has been created for "+
  					     "domain: " + domain);
  	}
      }
docs: Get the model mapped to by the given ModelDomain key.
  
  @param domain The ModelDomain object which keys to the desired model.
  @return The MaxentModel corresponding to the given domain.