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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 get_waveform_filter_length_in_time(approximant, template=None, **kwargs):
 """For filter templates, return the length in time of the template. """

    kwargs = props(template, **kwargs)

    if approximant in _filter_time_lengths:
        return _filter_time_lengths[approximant](**kwargs)
    else:
        return None