def make_tokens_dir(dir_, sources):
os.mkdir(tokens_dir + dir_)<EOL>for source in sources:<EOL><INDENT>if not os.path.isfile(corpora_dir + source):<EOL><INDENT>print('<STR_LIT>' + source)<EOL>return<EOL><DEDENT><DEDENT>with open(tokens_dir + dir_ + '<STR_LIT>', '<STR_LIT:w>') as outjson:<EOL><INDENT>json.dump(sources, outjson)<EOL><DEDENT>
Create a new directory named <dir_>. Create a new file within it called
    sources.json. The input <sources> is a list of names of tokenized texts.
    Write <sources> into sources.json.