human
Solve the following python programming problem given the following code:
def exec_save_classpath(logger, sbt_cmd, working_dir, classpath_file, classpath_log, callback_fn) : 
    '
    Run the sbt saveClasspath task (for starting the ensimeProcess) in a separate thread calling back
    with the result.
    :param sbt_cmd: The command for running sbt
    :param working_dir: The working directory to run in
    :param classpath_file: Where to write the classpath file to
    :param callback_fn: The function to call with the classpath (as a string)
    :return: Nothing
    ' 
    def worker() : 
        logger.info ('Save classpath task running') 
        cmd = (sbt_cmd + ['saveClasspath']) 
        with open (classpath_log, 'w') as output_file : 
            res = subprocess.call (cmd, cwd = working_dir, stdout = output_file, stderr = subprocess.STDOUT) 
            if (res == 0) : 
                with open (classpath_file, 'r') as f : 
                    read_classpath = f.read ().replace ('
', '') 
logger.info ('Save classpath task completed successfully') 
                callback_fn (read_classpath) 
else : 
                logger.info (((('Save classpath task failed with error ' + str (res)) + ' check ') + str (classpath_log))) 
                callback_fn (None) 
_thread.start_new_thread (logger, ()) 

    
    

    Fix the buggy line: _thread.start_new_thread (logger, ())
assistant
#Here is Python code to fix the buggy line: _thread.

_thread.start_new_thread (def worker(, ())