code: def create_graph_html(js_template, css_template, html_template=None):
      
      if html_template is None:
          html_template = read_lib('html', 'graph')
  
      # Create div ID for the graph and give it to the JS and CSS templates so
      # they can reference the graph.
      graph_id = 'graph-{0}'.format(_get_random_id())
      js = populate_template(js_template, graph_id=graph_id)
      css = populate_template(css_template, graph_id=graph_id)
  
      return populate_template(
          html_template,
          graph_id=graph_id,
          css=css,
          js=js
      )
docs: Create HTML code block given the graph Javascript and CSS.