code: def clean_cache(self, section=None):
          
          self.remove_all_locks()
          if section is not None and "/" in section:
              raise ValueError("invalid section '{0}'".format(section))
          if section is not None:
              path = os.path.join(self._full_base, section)
          else:
              path = self._full_base
          if not os.path.exists(path):
              return
          shutil.rmtree(path)
docs: Cleans the cache of this cache object.