<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
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<USER_TASK:>
Description:
 def get_all_keys(tweet, parent_key=''):
 """ 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: ['created_at', 'text', 'nested_field nested_1', 'nested_field nested_2'] """

    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