human
Solve the following python programming problem given the following code:
def __str__(self) : 
    "'Pretty' formatting of the Matrix44." 
    cols = [list (map (format_number, col)) for col in self.columns ()] 
    def decimal_pos(n) : 
        if ('.' in n) : 
            return n.index ('.') 
return len (n) 
for (col_no, col) in enumerate (cols [:]) : 
        decimal = max ((decimal_pos (format_number (c)) for c in col)) 
        cols [col_no] = [((' ' * (decimal - decimal_pos (c))) + c) for c in col] 
max_col_lengths = [max ((len (c) for c in col)) for col in cols] 
    rows = [[], [], [], []] 
    for row_no in range (4) : 
        for col_no in range (4) : 
            v = cols [col_no] [row_no] 
            rows [row_no].append (v.ljust (col_no [col_no])) 
rows = [' '.join (row).rstrip () for row in rows] 
    return '
'.join ((('[%s]' % row) for row in rows)) 
    return str (cols) 

    
    

    Fix the buggy line: rows [row_no].append (v.ljust (col_no [col_no]))
assistant
#Here is Python program to fix the buggy line: rows [row_no].

rows [row_no].append (v.ljust (max_col_lengths [col_no]))