human
Solve the following python programming problem given the following code:
def print_usage(self, cmd_name = None) : 
    'Print the usage(s) of all commands or a command.' 
    def append_usage(cmd_name, without_name = False) : 
        cmd_func = self.command_funcs [cmd_name] 
        usages.append (Command (cmd_func, cmd_name).build_usage (without_name)) 
usages = [] 
    if (cmd_name is None) : 
        if (self.default is not None) : 
            append_usage (self.default, True) 
for name in sorted (self.command_funcs.keys ()) : 
            append_usage (name) 
else : 
        if (self.default == cmd_name) : 
            append_usage (cmd_name, without_name = True) 
append_usage (cmd_name) 
iusages = iter (usages) 
    try : 
        print ('usage:', next (iusages)) 
except StopIteration : 
        pass 
else : 
        for usage in iusages : 
            print ('   or:', usage) 
if (cmd_name is None) : 
        if self.doc : 
            doc = self.doc 
else : 
            if inspect.ismodule (self.obj) : 
                doc = inspect.getdoc (self.obj) 
else : 
                doc = None 
if (not doc) : 
            cmd_name = self.default 
if cmd_name : 
        doc = inspect.getdoc (usage.command_funcs [cmd_name]) 
if doc : 
        print () 
        print (doc) 
        print () 

    
    

    Fix the buggy line: doc = inspect.getdoc (usage.command_funcs [cmd_name])
assistant
#Here is Python program to fix the buggy line: doc = inspect.

doc = inspect.getdoc (self.command_funcs [cmd_name])