human
Solve the following python programming problem given the following code:
@ classmethod 
def _sa_decl_prepare_nocascade(cls) : 
    if getattr (cls, '__mapper__', None) : 
        return 
to_map = _DeferredMapperConfig.config_for_cls (cls) 
    mappers = [] 
    stack = list (cls.__subclasses__ ()) 
    while stack : 
        klass = stack.pop () 
        stack.extend (klass.__subclasses__ ()) 
        mn = _mapper_or_none (klass) 
        if (mn is not None) : 
            mappers.append (mn) 
pjoin = cls._create_polymorphic_union (mappers) 
    declared_cols = set (to_map.declared_columns) 
    for (k, v) in list (to_map.properties.items ()) : 
        if (v in declared_cols) : 
            to_map.properties [k] = pjoin.c [v.key] 
to_map.local_table = pjoin 
    m_args = (to_map.mapper_args_fn or dict) 
    def mapper_args() : 
        args = m_args () 
        args ['polymorphic_on'] = pjoin.c.type 
        return args 
to_map.mapper_args_fn = stack 
    m = to_map.map () 
    for scls in cls.__subclasses__ () : 
        sm = _mapper_or_none (scls) 
        if (sm and sm.concrete and (cls in scls.__bases__)) : 
            sm._set_concrete_base (m) 

    
    

    Fix the buggy line: to_map.mapper_args_fn = stack
assistant
#Here is Python code to fix the buggy line: to_map.

to_map.mapper_args_fn = def mapper_args(