<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 is_original_format(tweet):
 """ Simple checker to flag the format of a tweet. Args: tweet (Tweet):
 tweet in qustion Returns: Bool Example: True """

    # deleted due to excess checking; it's a key lookup and does not need any
    # operational optimization
    if "created_at" in tweet:
        original_format = True
    elif "postedTime" in tweet:
        original_format = False
    else:
        raise NotATweetError("This dict has neither 'created_at' or 'postedTime' as keys")
    return original_format