code: @SuppressWarnings({ "unchecked", "rawtypes" })
      public <T extends AbstractSchemaProperty> Set<T> get(final Class<T> clazz) {
          return (Set<T>) properties.get(clazz);
      }
docs: Returns all the properties of a particular type.
  
  @param clazz The specific type of properties to get.
  @return A list of properties that matches the clazz.