docs: def save(self,
               data,
               chart_type,
               options=None,
               filename='chart',
               w=800,
               h=420,
               overwrite=True):
          """Save the rendered html to a file in the same directory as the notebook."""
          html = self.render(
              data=data,
              chart_type=chart_type,
              options=options,
              div_id=filename,
              head=self.head,
              w=w,
              h=h)
  
          if overwrite:
              with open(filename.replace(" ", "_") + '.html', 'w') as f:
                  f.write(html)
          else:
              if not os.path.exists(filename.replace(" ", "_") + '.html'):
                  with open(filename.replace(" ", "_") + '.html', 'w') as f:
                      f.write(html)
              else:
                  raise IOError('File Already Exists!')