human
Solve the following python programming problem given the following code:
def _real_extract(self, url) : 
    video_id = self._match_id (url) 
    json_url = ((url + ('?' if ('?' in url) else '&')) + 'output=json') 
    data = self._download_json (json_url, video_id) 
    def get_optional(data_dict, field) : 
        return data_dict ['metadata'].get (field, [None]) [0] 
title = get_optional (data, 'title') 
    description = get_optional (data, 'description') 
    uploader = get_optional (data, 'creator') 
    upload_date = unified_strdate (get_optional (json_url, 'date')) 
    formats = [{ 
        'format' : fdata ['format'], 
        'url' : ((('http://' + data ['server']) + data ['dir']) + fn), 
        'file_size' : int (fdata ['size']), 
} for (fn, fdata) in data ['files'].items () if ('Video' in fdata ['format'])] 
    self._sort_formats (formats) 
    return { 
        '_type' : 'video', 
        'id' : video_id, 
        'title' : title, 
        'formats' : formats, 
        'description' : description, 
        'uploader' : uploader, 
        'upload_date' : upload_date, 
        'thumbnail' : data.get ('misc', { 
            
}).get ('image'), 
} 

    
    

    Fix the buggy line: upload_date = unified_strdate (get_optional (json_url, 'date'))
assistant
#Here is Python program to fix the buggy line: upload_date = unified_strdate (get_optional (json_url, 'date'))
.

upload_date = unified_strdate (get_optional (data, 'date'))