code: def get(self, requirement):
          
          filename = self.generate_filename(requirement)
          for backend in list(self.backends):
              try:
                  pathname = backend.get(filename)
                  if pathname is not None:
                      return pathname
              except CacheBackendDisabledError as e:
                  logger.debug("Disabling %s because it requires configuration: %s", backend, e)
                  self.backends.remove(backend)
              except Exception as e:
                  logger.exception("Disabling %s because it failed: %s", backend, e)
                  self.backends.remove(backend)
docs: Get a distribution archive from any of the available caches.
  
          :param requirement: A :class:`.Requirement` object.
          :returns: The absolute pathname of a local file or :data:`None` when the
                    distribution archive is missing from all available caches.