code: public Optional<Maker<?>> getMaker(Settable settable) {
          for (Matcher<?> matcher : makers.keySet()) {
              if (matcher.matches(settable.fullyQualifiedName())) {
                  return Optional.<Maker<?>>of(makers.get(matcher));
              }
          }
          return Optional.absent();
      }
docs: Try to get a registered maker for a settable.
  It will use the key (Matcher) to match com.github.huangp.entityunit.util.Settable#fullyQualifiedName(),
  if there is a match found, it will return that.
  
  @param settable
  settable
  @return Optional maker