docs: def cache_clear(self):
          """Clear local cache by deleting all cached resources and their
          downloaded files.
          """
          # Delete content of local cache directory
          for f in os.listdir(self.directory):
              f = os.path.join(self.directory, f)
              if os.path.isfile(f):
                  os.remove(f)
              elif os.path.isdir(f):
                  shutil.rmtree(f)
          # Empty cache index
          self.cache = {}