code: def resolve_nested_dict(nested_dict):
      
      res = {}
      for k, v in nested_dict.items():
          if isinstance(v, dict):
              for k_, v_ in resolve_nested_dict(v).items():
                  res[(k, ) + k_] = v_
          else:
              res[(k, )] = v
      return res
docs: Flattens a nested dict by joining keys into tuple of paths.
  
      Can then be passed into `format_vars`.