human
Solve the following python programming problem given the following code:
def autoload_filenode(must_be = None, default_root = False) : 
    'Implies both must_have_addon osfstorage node and
    handle_odm_errors
    Attempts to load fid as a OsfStorageFileNode with viable constraints
    ' 
    def _autoload_filenode(func) : 
        @ handle_odm_errors 
        @ must_have_addon ('osfstorage', 'node') 
        @ functools.wraps (func) 
        def wrapped(* args, **kwargs) : 
            node = kwargs ['node'] 
            if (('fid' not in kwargs) and default_root) : 
                file_node = kwargs ['node_addon'].get_root () 
else : 
                file_node = models.OsfStorageFileNode.get (kwargs.get ('fid'), node) 
if (must_be and (file_node.kind != must_be)) : 
                raise HTTPError (httplib.BAD_REQUEST, data = { 
                    'message_short' : 'incorrect type', 
                    'message_long' : 'FileNode must be of type {} not {}'.format (must_be, file_node.kind), 
}) 
kwargs ['file_node'] = file_node 
            return func (* args, ** kwargs) 
return wrapped 
return <MASK> 
    
    Given the code above, what is a proper replacement for <MASK>? Choose among: default_root, must_be
assistant
#Here is a proper replacement for <MASK>.
def _autoload_filenode(