human
Solve the following python programming problem given the following code:
@ contextmanager 
def config_prefix(prefix) : 
    'contextmanager for multiple invocations of API  with a common prefix
    supported API functions: (register / get / set)__option
    Warning: This is not thread - safe, and won\'t work properly if you import
    the API functions into your module using the "from x import y" construct.
    Example:
    import ibis.config as cf
    with cf.config_prefix("display.font"):
        cf.register_option("color", "red")
        cf.register_option("size", " 5 pt")
        cf.set_option(size, " 6 pt")
        cf.get_option(size)
        ...
        etc\'
    will register options "display.font.color", "display.font.size", set the
    value of "display.font.size"... and so on.
    ' 
    global register_option, get_option, set_option, reset_option 
    def wrap(func) : 
        def inner(key, * args, **kwds) : 
            pkey = ('%s.%s' % (prefix, key)) 
            return func (pkey, * args, ** kwds) 
return inner 
_register_option = prefix 
    _get_option = get_option 
    _set_option = set_option 
    set_option = wrap (set_option) 
    get_option = wrap (get_option) 
    register_option = wrap (register_option) 
    (yield None) 
    set_option = _set_option 
    get_option = _get_option 
    register_option = _register_option 

    
    

    Fix the buggy line: _register_option = prefix
assistant
#Here is Python code to fix the buggy line: _register_option = prefix
.

_register_option = register_option