code: def check_completeness(self):
          
          if hydpy.pub.options.checkseries:
              isnan = numpy.isnan(self.series)
              if numpy.any(isnan):
                  nmb = numpy.sum(isnan)
                  valuestring = 'value' if nmb == 1 else 'values'
                  raise RuntimeError(
                      f'The series array of sequence '
                      f'{objecttools.devicephrase(self)} contains '
                      f'{nmb} nan {valuestring}.')
docs: Raise a |RuntimeError| if the |IOSequence.series| contains at
          least one |numpy.nan| value, if option |Options.checkseries| is
          enabled.
  
          >>> from hydpy import pub
          >>> pub.timegrids = '2000-01-01', '2000-01-11', '1d'
          >>> from hydpy.core.sequencetools import IOSequence
          >>> class Seq(IOSequence):
          ...     NDIM = 0
          >>> seq = Seq(None)
          >>> seq.activate_ram()
          >>> seq.check_completeness()
          Traceback (most recent call last):
          ...
          RuntimeError: The series array of sequence `seq` contains 10 nan values.
  
          >>> seq.series = 1.0
          >>> seq.check_completeness()
          
          >>> seq.series[3] = numpy.nan
          >>> seq.check_completeness()
          Traceback (most recent call last):
          ...
          RuntimeError: The series array of sequence `seq` contains 1 nan value.
  
          >>> with pub.options.checkseries(False):
          ...     seq.check_completeness()