human
Solve the following python programming problem given the following code:
def pp_options_list(keys, width = 80, _print = False) : 
    ' Builds a concise listing of available options, grouped by prefix ' 
    from textwrap import wrap 
    from itertools import groupby 
    def pp(name, ks) : 
        pfx = ((('- ' + name) + '.[') if name else '') 
        ls = wrap (', '.join (ks), width, initial_indent = pfx, subsequent_indent = '  ', break_long_words = False) 
        if (ls and ls [(- 1)] and name) : 
            ls [(- 1)] = (ls [(- 1)] + ']') 
return ls 
ls = [] 
    singles = [g for x in sorted (keys) if (x.find ('.') < 0)] 
    if singles : 
        ls += pp ('', singles) 
keys = [x for x in keys if (x.find ('.') >= 0)] 
    for (k, g) in groupby (sorted (keys), (lambda x : x [: x.rfind ('.')])) : 
        ks = [x [(len (k) + 1) :] for x in list (g)] 
        ls += pp (k, ks) 
s = '
'.join (ls) 
    if _print : 
        print (s) 
else : 
        return s 

    
    

    Fix the buggy line: singles = [g for x in sorted (keys) if (x.find ('.') < 0)]
assistant
#Here is Python code to find ('.

singles = [x for x in sorted (keys) if (x.find ('.') < 0)]