human
Complete this python program:
def _os_bootstrap():
assistant
#Here is the Python code you requested.

    """Set up \os\ module replacement functions for use during import bootstrap.
    """
    global _os_path_join
    global _os_stat
    names = sys.builtin_module_names
    join = None
    if ('posix' in names):
        sep = '/'
        from posix import stat
    elif ('nt' in names):
        sep = '\\'
        from nt import stat
    elif ('dos' in names):
        sep = '\\'
        from dos import stat
    elif ('os2' in names):
        sep = '\\'
        from os2 import stat
    else:
        raise ImportError, 'no    os    specific    module    found'
    if (join is None):
        def join(a, b, sep=sep):
            if (a == ''):
                return b
            lastchar = a[(-1):]
            if ((lastchar == '/') or (lastchar == sep)):
                return (a + b)
            return ((a + sep) + b)
    _os_stat = stat
    _os_path_join = join
    return