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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def prune(self, vault_client):
 """Will remove any mount point which is not actually defined in this context. """

        existing = getattr(vault_client,
                           SecretBackend.list_fun)()['data'].items()
        for mount_name, _values in existing:
            # ignore system paths and cubbyhole
            mount_path = normalize_vault_path(mount_name)
            if mount_path.startswith('sys') or mount_path == 'cubbyhole':
                continue

            exists = [resource.path
                      for resource in self.mounts()
                      if normalize_vault_path(resource.path) == mount_path]

            if not exists:
                LOG.info("removed unknown mount %s", mount_path)
                getattr(vault_client, SecretBackend.unmount_fun)(mount_path)