docs: def dict_merge(s, m):
      """Recursively merge one dict into another."""
      if not isinstance(m, dict):
          return m
      out = copy.deepcopy(s)
      for k, v in m.items():
          if k in out and isinstance(out[k], dict):
              out[k] = dict_merge(out[k], v)
          else:
              out[k] = copy.deepcopy(v)
      return out