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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 tropical_nights(tasmin, thresh='20.0 degC', freq='YS'):
 r"""Tropical nights The number of days with minimum daily temperature above threshold. Parameters tasmin : xarray.DataArray Minimum daily temperature [℃] or [K] thresh : str Threshold temperature on which to base evaluation [℃] or [K]. Default: '20 degC'. freq : str, optional Resampling frequency Returns ------- xarray.DataArray Number of days with minimum daily temperature above threshold. Notes ----- Let :math:`TN_{ij}` be the daily minimum temperature at day :math:`i` of period :math:`j`. Then counted is the number of days where: .. math:: TN_{ij} > Threshold [℃] """

    thresh = utils.convert_units_to(thresh, tasmin)
    return tasmin.pipe(lambda x: (tasmin > thresh) * 1) \
        .resample(time=freq) \
        .sum(dim='time')