code: public void setTemplateResolver(final ITemplateResolver templateResolver) {
          Validate.notNull(templateResolver, "Template Resolver cannot be null");
          checkNotInitialized();
          this.templateResolvers.clear();
          this.templateResolvers.add(templateResolver);
      }
docs: <p>
  Sets a single template resolver for this template engine.
  </p>
  <p>
  Calling this method is equivalent to calling {@link #setTemplateResolvers(Set)}
  passing a Set with only one template resolver.
  </p>
  
  @param templateResolver the template resolver to be set.