code: def _path_for_file(self, project_name, date):
          
          return os.path.join(
              self.cache_path,
              '%s_%s.json' % (project_name, date.strftime('%Y%m%d'))
          )
docs: Generate the path on disk for a specified project and date.
  
          :param project_name: the PyPI project name for the data
          :type project: str
          :param date: the date for the data
          :type date: datetime.datetime
          :return: path for where to store this data on disk
          :rtype: str