docs: def get_temp_dimname(dims: Container[Hashable], new_dim: Hashable) -> Hashable:
      """ Get an new dimension name based on new_dim, that is not used in dims.
      If the same name exists, we add an underscore(s) in the head.
  
      Example1:
          dims: ['a', 'b', 'c']
          new_dim: ['_rolling']
          -> ['_rolling']
      Example2:
          dims: ['a', 'b', 'c', '_rolling']
          new_dim: ['_rolling']
          -> ['__rolling']
      """
      while new_dim in dims:
          new_dim = '_' + str(new_dim)
      return new_dim