human
Solve the following python programming problem given the following code:
@ feature ('dlrun') 
def feature_dlrun(tgen) : 
    '
    Download a file.
    ' 
    work_dir = tgen.make_node (tgen.worch.dlrun_dir) 
    tgen.step ('dlrun_seturl', rule = ("echo '%s' > %s" % (tgen.worch.dlrun_url, tgen.worch.dlrun_urlfile)), update_outputs = True, target = tgen.worch.dlrun_urlfile) 
    def dl_task(task) : 
        src = task.inputs [0] 
        tgt = task.outputs [0] 
        url = src.read ().strip () 
        try : 
            web = urlopen (url) 
            tgt.write (web.read (), 'wb') 
except Exception : 
            import traceback 
            traceback.print_exc () 
            msg.error (tgen.worch.format ('error downloading {dlrun_url}')) 
            raise 
checksum = tgen.worch.dlrun_checksum 
        if (not checksum) : 
            return 
(hasher_name, ref) = checksum.split (':') 
        import hashlib, os 
        hasher = getattr (hashlib, hasher_name) () 
        hasher.update (tgt.read ('rb')) 
        data = hasher.hexdigest () 
        if (data != ref) : 
            msg.error (tgen.worch.format (('invalid checksum:
ref: %s
new: %s' % (ref, data)))) 
            try : 
                os.remove (tgt.abspath ()) 
except IOError : 
                pass 
return 1 
return 
script = work_dir.make_node (tgen.worch.dlrun_target) 
    tgen.step ('dldownload', rule = dl_task, source = tgen.worch.dlrun_urlfile, target = script, cwd = work_dir.abspath ()) 
    cmd_rule = tgen.worch.format ('chmod +x {dlrun_cmd} && ./{dlrun_cmd} {dlrun_cmd_options}') 
    tgen.step ('dlcommand', rule = cmd_rule, source = cmd_rule, target = map (work_dir.make_node, tgen.to_list (tgen.worch.dlrun_cmd_target)), cwd = work_dir.abspath ()) 
    return 

    
    

    Fix the buggy line: tgen.step ('dlcommand', rule = cmd_rule, source = cmd_rule, target = map (work_dir.make_node, tgen.to_list (tgen.worch.dlrun_cmd_target)), cwd = work_dir.abspath ())
assistant
#Here is Python program to fix the buggy line: tgen.

tgen.step ('dlcommand', rule = cmd_rule, source = script, target = map (work_dir.make_node, tgen.to_list (tgen.worch.dlrun_cmd_target)), cwd = work_dir.abspath ())