docs: def available_features(rtdc_ds):
          """Determine available features for an RT-DC dataset
  
          Parameters
          ----------
          rtdc_ds: instance of RTDCBase
              The dataset to check availability for
  
          Returns
          -------
          features: dict
              Dictionary with feature names as keys and instances
              of `AncillaryFeature` as values.
          """
          cols = {}
          for inst in AncillaryFeature.features:
              if inst.is_available(rtdc_ds):
                  cols[inst.feature_name] = inst
          return cols