human
Solve the following python programming problem given the following code:
def flat(files, config) : 
    outroot = os.path.join (config ['root'], outfile_for ['output'] ['dir']) 
    def outfile_for(infile) : 
        outname = os.path.basename ((os.path.splitext (infile) [0] + '.css')) 
        return os.path.join (outroot, outname) 
return _compile (files, config, outfile_for) 

    
    

    Fix the buggy line: outroot = os.path.join (config ['root'], outfile_for ['output'] ['dir'])
assistant
#Here is Python code to fix the buggy line: outroot = os.

outroot = os.path.join (config ['root'], config ['output'] ['dir'])