human
Complete the below
def _subst_vars(path, local_vars):

    ''''In the string `path`, replace tokens like {some.thing} with the
    corresponding value from the map `local_vars`.
    If there is no corresponding value, leave the token unchanged.'
    '''
 ... Give me a the Python program you requested?
assistant
#Here is the Python program you requested.
    def _replacer(matchobj):
        name = matchobj.group(1)
        if (name in local_vars):
            return local_vars[name]
        elif (name in os.environ):
            return os.environ[name]
        return matchobj.group(0)
    return _VAR_REPL.sub(_replacer, path)