def export_to_file(filename, options={})
      content_string = export_to_string(default_options(filename).merge(:filename => filename))
      File.open(filename, "w") { |f| f.write(content_string) }
      nil
    end
def export_to_file(filename, options={})
      content_string = export_to_string(default_options(filename).merge(:filename => filename))
      File.open(filename, "w") { |f| f.write(content_string) }
      nil
    end
Export this map to the given filename in the appropriate format.

 @param filename [String] The file path to export to
 @param options [Hash] Options for exporting
 @option options [Symbol] format The format to export to, such as :tmx or :json
 @return [void]