docs: public TemplateVariables concat(Collection<TemplateVariable> variables) {
  
  		List<TemplateVariable> result = new ArrayList<>(this.variables.size() + variables.size());
  		result.addAll(this.variables);
  
  		List<TemplateVariable> filtered = variables.stream() //
  				.filter(variable -> !containsEquivalentFor(variable)).collect(Collectors.toList());
  
  		result.addAll(filtered);
  
  		return new TemplateVariables(result);
  	}