code: def html(self):
          
          ret_code = self._sphinx_build('html')
          zip_fname = os.path.join(BUILD_PATH, 'html', 'pandas.zip')
          if os.path.exists(zip_fname):
              os.remove(zip_fname)
  
          if self.single_doc_html is not None:
              self._open_browser(self.single_doc_html)
          else:
              self._add_redirects()
          return ret_code
docs: Build HTML documentation.