How to traverse the json document with cypher if i don't know the key names

How to access the keys in a json document using cypher to create graph database when i don't know their names or they are arbitrary

{
    "934934507945312256": {
        "quote_count": 0, 
        "reply_count": 0, 
        "hashtags": null, 
        "datetime": "2017-11-26 23:58:51", 
        "date": "2017-11-26", 
        "like_count": 0, 
        "verified": "False", 
        "sentiment": 0, 
        "author": "Judy💯The Resistance", 
        "location": "Hollywood, California USA🇺🇸", 
        "tid": "934934507945312256", 
        "retweet_count": 0, 
        "type": "retweet", 
        "media_list": null, 
        "quoted_source_id": null, 
        "url_list": null, 
        "tweet_text": "RT @kylegriffin1: Reminder: The Senate Judiciary Committee gave Jared Kushner a November 27 deadline to turn over the missing records… ", 
        "author_profile_image": "https://pbs.twimg.com/profile_images/922041668496265216/uV8jwota_normal.jpg", 
        "author_screen_name": "jgirl66", 
        "author_id": "23737528", 
        "lang": "en", 
        "keywords_processed_list": [
            "reminder", 
            "senate judiciary committee", 
            "kushner november", 
            "deadline"
        ], 
        "retweet_source_id": "934872065471115264", 
        "mentions": [
            "kylegriffin1"
        ], 
        "replyto_source_id": null
    }, 
    "934933403232714752": {
        "quote_count": 0, 
        "reply_count": 0, 
        "hashtags": null, 
        "datetime": "2017-11-26 23:54:28", 
        "date": "2017-11-26", 
        "like_count": 0, 
        "verified": "True", 
        "sentiment": 0, 
        "author": "GibsonVernacular.com", 
        "location": "Bay Area ✈ Los Angeles ", 
        "tid": "934933403232714752", 
        "retweet_count": 0, 
        "type": "retweet", 
        "media_list": null, 
        "quoted_source_id": null, 
        "url_list": null, 
        "tweet_text": "RT @kylegriffin1: Reminder: The Senate Judiciary Committee gave Jared Kushner a November 27 deadline to turn over the missing records… ", 
        "author_profile_image": "https://pbs.twimg.com/profile_images/851148627732865026/lP5uWcjn_normal.jpg", 
        "author_screen_name": "LuciusGibson", 
        "author_id": "60775653", 
        "lang": "en", 
        "keywords_processed_list": [
            "reminder", 
            "senate judiciary committee", 
            "kushner november", 
            "deadline"
        ], 
        "retweet_source_id": "934872065471115264", 
        "mentions": [
            "kylegriffin1"
        ], 
        "replyto_source_id": null
    }
 
}

In this JSON file i want to first access the key "934934507945312256" and the inside it. And after that this key "934933403232714752" and data corresponding to it.
But after using the unwind option i am unable to access the key.
Because this key value is randomly generated so,i cannot know the value beforehand how can i access these values and data inside it.

here's what i have tried

WITH {json} AS document
        UNWIND document AS category
        FOREACH (l in category |
        MERGE (label:ho{author:l.author}))

But i am getting this error:-

Cannot merge node using null property value for author

What should i do? How can i access the values inside the keys.