code: def get_all_keys(tweet, parent_key=''):
      
      items = []
      for k, v in tweet.items():
          new_key = parent_key + " " + k
          if isinstance(v, dict):
              items.extend(get_all_keys(v, parent_key=new_key))
          else:
              items.append(new_key.strip(" "))
      return items
docs: Takes a tweet object and recursively returns a list of all keys contained
      in this level and all nexstted levels of the tweet.
  
      Args:
          tweet (Tweet): the tweet dict
          parent_key (str): key from which this process will start, e.g., you can
                            get keys only under some key that is not the top-level key.
  
      Returns:
          list of all keys in nested dicts.
  
      Example:
          >>> import tweet_parser.tweet_checking as tc
          >>> tweet = {"created_at": 124125125125, "text": "just setting up my twttr",
          ...          "nested_field": {"nested_1": "field", "nested_2": "field2"}}
          >>> tc.get_all_keys(tweet)
          ['created_at', 'text', 'nested_field nested_1', 'nested_field nested_2']