/// If the iterators start and finish point to the same map and last is reachable from first, all elements in the range [start, finish) are deleted from the map.
virtual void erase(iterator start, iterator finish)
{_base.erase(start, finish);}
/// Deletes the element with the key value x from the map, if one exists. Returns 1 if x existed in the map, 0 otherwise.
virtual size_type erase(const key_type& x)
{return _base.erase(x);}
/// Deletes the map element pointed to by the iterator position.
virtual void erase(iterator position)
{_base.erase(position);}
