code: def export_to_string(options = {})
        hash = self.to_h
  
        # Need to add back all non-tilelayers to hash["layers"]
        image_layers = hash.delete(:image_layers)
        object_groups = hash.delete(:object_groups)
        hash[:layers] += image_layers
        hash[:layers] += object_groups
        hash[:layers].sort_by! { |l| l[:name] }
        hash.delete(:contents)
  
        object_groups.each do |object_layer|
          object_layer["objects"].each do |object|
            # If present, "shape" and "points" should be removed
            object.delete("shape")
            object.delete("points")
          end
        end
  
        MultiJson.dump(hash)
      end
docs: Export this map as a string in the appropriate format.
  
   @param options [Hash] Options for exporting
   @option options [Symbol,String] :format The format to export to, such as :tmx or :json
   @option options [String] :filename The eventual filename, which gives a relative path for linked TSX files
   @return [String] The exported content in the appropriate format