code: @Override
      public boolean containsValue(Object value) {
  	// Overridden to take advantage of faster iterator
  	if (value == null) {
  	    for (Entry e = header.after; e != header; e = e.after)
  		if (e.value == null) return true;
  	}
  	else {
  	    for (Entry e = header.after; e != header; e = e.after)
  		if (value.equals(e.value)) return true;
  	}
  	return false;
      }
docs: Returns <tt>true</tt> if this map maps one or more keys to the specified value.
  
  @param value value whose presence in this map is to be tested
  @return <tt>true</tt> if this map maps one or more keys to the specified value