code: def remove_once(gset, elem):
      
      remove = getattr(gset, 'remove', None)
      if remove is not None: remove(elem)
      else: del gset[elem]
      return elem
docs: Remove the element from a set, lists or dict.
      
          >>> L = ["Lucy"]; S = set(["Sky"]); D = { "Diamonds": True };
          >>> remove_once(L, "Lucy"); remove_once(S, "Sky"); remove_once(D, "Diamonds");
          >>> print L, S, D
          [] set([]) {}
  
      Returns the element if it was removed. Raises one of the exceptions in 
      :obj:`RemoveError` otherwise.