code: def clear_cache(self, back=None):
          '''
          Clear the cache of all of the fileserver backends that support the
          clear_cache function or the named backend(s) only.
          '''
          back = self.backends(back)
          cleared = []
          errors = []
          for fsb in back:
              fstr = '{0}.clear_cache'.format(fsb)
              if fstr in self.servers:
                  log.debug('Clearing %s fileserver cache', fsb)
                  failed = self.servers[fstr]()
                  if failed:
                      errors.extend(failed)
                  else:
                      cleared.append(
                          'The {0} fileserver cache was successfully cleared'
                          .format(fsb)
                      )
          return cleared, errorf clear_cache(self, back=None):
          '''
          Clear the cache of all of the fileserver backends that support the
          clear_cache function or the named backend(s) only.
          '''
          back = self.backends(back)
          cleared = []
          errors = []
          for fsb in back:
              fstr = '{0}.clear_cache'.format(fsb)
              if fstr in self.servers:
                  log.debug('Clearing %s fileserver cache', fsb)
                  failed = self.servers[fstr]()
                  if failed:
                      errors.extend(failed)
                  else:
                      cleared.append(
                          'The {0} fileserver cache was successfully cleared'
                          .format(fsb)
                      )
          return cleared, errors
docs: Clear the cache of all of the fileserver backends that support the
          clear_cache function or the named backend(s) only.