docs: def _link(self, base_dir: str, artifact_map: dict, conf: Config):
          """Link all artifacts in `artifact_map` under `base_dir` and return
             the number of artifacts linked."""
          num_linked = 0
          for dst, src in artifact_map.items():
              abs_src = join(conf.project_root, src)
              abs_dest = join(conf.project_root, base_dir, dst)
              link_node(abs_src, abs_dest)
              num_linked += 1
          return num_linked