docs: def path_serialize(cls, path):
          """
          Given a list of [{'hash': ..., 'order': ...}], serialize it to a string.
          """
          # make it into a netstring
          path_parts = ['{}-{}'.format(p['order'], p['hash']) for p in path]
          path_ns_parts = ['{}:{},'.format(len(pp), pp) for pp in path_parts]
          path_str = ''.join(path_ns_parts)
          return '{}:{},'.format(len(path_str), path_str)