def to_json(options = nil)
      mapper = (options.nil? || !options.key?(:mapper))? self.class.mapper: options[:mapper]
      object = (options.nil? || !options.key?(:object))? self: options[:object]
      serialize(mapper, object)
    end
def to_json(options = nil)
      mapper = (options.nil? || !options.key?(:mapper))? self.class.mapper: options[:mapper]
      object = (options.nil? || !options.key?(:object))? self: options[:object]
      serialize(mapper, object)
    end
Serialize the object to JSON
 @param options [Hash] hash map contains options to convert to json.
 @return [String] JSON serialized version of the object