human
Solve the following python programming problem given the following code:
def func(self) : 
    'Implements the spawner' 
    def _show_prototypes(prototypes) : 
        'Helper to show a list of available prototypes' 
        string = '
Available prototypes:
 %s' 
        string = (string % utils.fill (', '.join (sorted (prototypes.keys ())))) 
        return string 
prototypes = spawn (return_prototypes = True) 
    if (not self.args) : 
        string = 'Usage: @spawn {key:value, key, value, ... }' 
        self.caller.msg ((obj + _show_prototypes (prototypes))) 
        return 
try : 
        prototype = _convert_from_string (self, self.args) 
except SyntaxError : 
        string = '{RCritical Python syntax error in argument. ' 
        string += 'Only primitive Python structures are allowed. ' 
        string += '
You also need to use correct Python syntax. ' 
        string += 'Remember especially to put quotes around all ' 
        string += 'strings inside lists and dicts.{n' 
        self.caller.msg (string) 
        return 
if isinstance (prototype, basestring) : 
        keystr = prototype 
        prototype = prototypes.get (prototype, None) 
        if (not prototype) : 
            string = ("No prototype named '%s'." % keystr) 
            self.caller.msg ((string + _show_prototypes (prototypes))) 
            return 
else : 
        if (not isinstance (prototype, dict)) : 
            self.caller.msg ('The prototype must be a prototype key or a Python dictionary.') 
            return 
if ((not ('noloc' in self.switches)) and (not ('location' in prototype))) : 
        prototype ['location'] = self.caller.location 
for obj in spawn (prototype) : 
        self.caller.msg (('Spawned %s.' % obj.get_display_name (self.caller))) 

    
    

    Fix the buggy line: self.caller.msg ((obj + _show_prototypes (prototypes)))
assistant
#Here is Python code to fix the buggy line: self.

self.caller.msg ((string + _show_prototypes (prototypes)))