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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def prepare_query_params(**kwargs):
 """ Prepares given parameters to be used in querystring. """

    return [
        (sub_key, sub_value)
        for key, value in kwargs.items()
        for sub_key, sub_value in expand(value, key)
        if sub_value is not None
    ]