human
Solve the following python programming problem given the following code:
def patch_thread_ident() : 
    if getattr (patch_thread_ident, 'called', False) : 
        return 
try : 
        from django.db.backends import BaseDatabaseWrapper, DatabaseError 
        if ('validate_thread_sharing' in BaseDatabaseWrapper.__dict__) : 
            import thread 
            _get_ident = thread.get_ident 
            __old__init__ = BaseDatabaseWrapper.__init__ 
            def _init(self, * args, **kwargs) : 
                __old__init__ (self, * args, ** kwargs) 
                self._thread_ident = _get_ident () 
def _validate_thread_sharing(self) : 
                if ((not self.allow_thread_sharing) and (self._thread_ident != _get_ident ())) : 
                    raise DatabaseError ((DB_SHARED_THREAD % (self.alias, self._thread_ident, _get_ident ()))) 
BaseDatabaseWrapper.__init__ = _init 
            BaseDatabaseWrapper.validate_thread_sharing = <MASK> 
patch_thread_ident.called = True 
except ImportError : 
        pass 
    
    Given the code above, what is a proper replacement for <MASK>? Choose among: _get_ident, __old__init__, _init
assistant
#Here is a proper replacement for <MASK>.
def _validate_thread_sharing(