.        *  Note that this function only erases the element, and that if        *  the element is itself a pointer, the pointed-to memory is not touched        *  in any way.  Managing the pointer is the user's responsibility.        */       size_type       erase(const key_type& __x)       { return _M_h.erase(__x); }        /**        *  @brief Erases a [__first,__last) range of elements from an        *  %unordered_set.        *  @param  __first  Iterator pointing to the start of the range to be        *                  erased.        *  @param __last  Iterator pointing to the end of the range to        *                be erased.        *  @return The iterator @a __last.        *        *  This function erases a sequence of elements from an 