@Override
  public boolean getAllPossibleValues(List<Completion> completions, Class<?> targetType,
      String existingData, String optionContext, MethodTarget target) {
    return false;
  }
Used by Gfsh command options that converts a string to a ClassName Object

User can specify either a classname alone or a className followed by a "?" and json properties to
initialize the object

e.g. --cache-loader=my.app.CacheLoader
--cache-loader=my.app.CacheLoader?{"param1":"value1","param2":"value2"}

Currently, if you specify a json properties after the className, the class needs to be a
Declarable for it to be initialized, otherwise, the properties are ignored.
geode-gfsh/src/main/java/org/apache/geode/management/internal/cli/converters/ClassNameConverter.java