def load_js(element_id)
      language_opt = ", language: '#{language}'" if language

      "\n  google.load('visualization', '#{version}', {packages: ['#{package_name}']#{language_opt}, callback: #{chart_function_name(element_id)}});"
    end
Generates JavaScript for loading the appropriate Google Visualization package, with callback to render chart.

Parameters:
*div_id            [Required] The ID of the DIV element that the Google Chart should be rendered in.