code: def get_too_few_non_zero_degree_day_warning(
      model_type, balance_point, degree_day_type, degree_days, minimum_non_zero
  ):
      
      warnings = []
      n_non_zero = int((degree_days > 0).sum())
      if n_non_zero < minimum_non_zero:
          warnings.append(
              EEMeterWarning(
                  qualified_name=(
                      "eemeter.caltrack_daily.{model_type}.too_few_non_zero_{degree_day_type}".format(
                          model_type=model_type, degree_day_type=degree_day_type
                      )
                  ),
                  description=(
                      "Number of non-zero daily {degree_day_type} values below accepted minimum."
                      " Candidate fit not attempted.".format(
                          degree_day_type=degree_day_type.upper()
                      )
                  ),
                  data={
                      "n_non_zero_{degree_day_type}".format(
                          degree_day_type=degree_day_type
                      ): n_non_zero,
                      "minimum_non_zero_{degree_day_type}".format(
                          degree_day_type=degree_day_type
                      ): minimum_non_zero,
                      "{degree_day_type}_balance_point".format(
                          degree_day_type=degree_day_type
                      ): balance_point,
                  },
              )
          )
      return warnings
docs: Return an empty list or a single warning wrapped in a list regarding
      non-zero degree days for a set of degree days.
  
      Parameters
      ----------
      model_type : :any:`str`
          Model type (e.g., ``'cdd_hdd'``).
      balance_point : :any:`float`
          The balance point in question.
      degree_day_type : :any:`str`
          The type of degree days (``'cdd'`` or ``'hdd'``).
      degree_days : :any:`pandas.Series`
          A series of degree day values.
      minimum_non_zero : :any:`int`
          Minimum allowable number of non-zero degree day values.
  
      Returns
      -------
      warnings : :any:`list` of :any:`eemeter.EEMeterWarning`
          Empty list or list of single warning.