code: protected void validateProduces(Collection<String> contentTypes) {
          Set<String> ignoreProduces = new TreeSet<>();
          ignoreProduces.add(Produces.TEXT);
          ignoreProduces.add(Produces.HTML);
          ignoreProduces.add(Produces.XHTML);
  
          for (String produces : declaredProduces) {
              if (ignoreProduces.contains(produces)) {
                  continue;
              }
  
              if (!contentTypes.contains(produces)) {
                  throw new PippoRuntimeException("{} declares @{}(\"{}\") but there is no registered ContentTypeEngine for that type!",
                          LangUtils.toString(controllerMethod), Produces.class.getSimpleName(), produces);
              }
          }
      }
docs: Validates that the declared content-types can actually be generated by Pippo.
  
  @param contentTypes